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	$183.58	9.678%	$201.3469	$201.35	$201.35	$201.30
Purchase #2	$182.45	7.506%	$196.1447	$196.14	$196.15	$196.10
Purchase #3	$245.64	13.328%	$278.3789	$278.38	$278.40	$278.40
Purchase #4	$149.47	11.143%	$166.1254	$166.13	$166.15	$166.10
Purchase #5	$54.61	9.627%	$59.8673	$59.87	$59.85	$59.90
Purchase #6	$81.39	10.335%	$89.8017	$89.80	$89.80	$89.80
Purchase #7	$145.26	7.475%	$156.1182	$156.12	$156.10	$156.10
7 purchase totals =	$1,042.40		$1,147.7831	$1,147.79	$1,147.80	$1,147.70