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	$179.58	10.777%	$198.9333	$198.93	$198.95	$198.90
Purchase #2	$173.44	4.785%	$181.7391	$181.74	$181.75	$181.70
Purchase #3	$112.57	9.658%	$123.442	$123.44	$123.45	$123.40
Purchase #4	$190.69	7.525%	$205.0394	$205.04	$205.05	$205.00
Purchase #5	$162.58	7.134%	$174.1785	$174.18	$174.20	$174.20
Purchase #6	$90.47	10.196%	$99.6943	$99.69	$99.70	$99.70
Purchase #7	$48.25	6.626%	$51.447	$51.45	$51.45	$51.40
7 purchase totals =	$957.58		$1,034.4736	$1,034.47	$1,034.55	$1,034.30