Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$210.63	9.575%	$230.7978	$230.80	$230.80	$230.80
Purchase #2	$165.30	12.179%	$185.4319	$185.43	$185.45	$185.40
Purchase #3	$187.97	12.685%	$211.814	$211.81	$211.80	$211.80
Purchase #4	$102.78	4.597%	$107.5048	$107.50	$107.50	$107.50
Purchase #5	$236.33	11.362%	$263.1818	$263.18	$263.20	$263.20
Purchase #6	$185.93	5.641%	$196.4183	$196.42	$196.40	$196.40
Purchase #7	$155.29	4.792%	$162.7315	$162.73	$162.75	$162.70
7 purchase totals =	$1,244.23		$1,357.8801	$1,357.87	$1,357.90	$1,357.80