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	$238.31	7.515%	$256.219	$256.22	$256.20	$256.20
Purchase #2	$53.67	10.681%	$59.4025	$59.40	$59.40	$59.40
Purchase #3	$188.94	5.809%	$199.9155	$199.92	$199.90	$199.90
Purchase #4	$113.67	5.832%	$120.2992	$120.30	$120.30	$120.30
Purchase #5	$87.28	3.542%	$90.3715	$90.37	$90.35	$90.40
Purchase #6	$205.74	5.533%	$217.1236	$217.12	$217.10	$217.10
Purchase #7	$196.72	7.716%	$211.8989	$211.90	$211.90	$211.90
7 purchase totals =	$1,084.33		$1,155.2302	$1,155.23	$1,155.15	$1,155.20