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	$93.41	6.531%	$99.5106	$99.51	$99.50	$99.50
Purchase #2	$153.26	4.181%	$159.6678	$159.67	$159.65	$159.70
Purchase #3	$99.94	3.568%	$103.5059	$103.51	$103.50	$103.50
Purchase #4	$117.52	10.653%	$130.0394	$130.04	$130.05	$130.00
Purchase #5	$154.61	10.693%	$171.1424	$171.14	$171.15	$171.10
Purchase #6	$238.78	5.499%	$251.9105	$251.91	$251.90	$251.90
Purchase #7	$86.33	9.356%	$94.407	$94.41	$94.40	$94.40
7 purchase totals =	$943.85		$1,010.1836	$1,010.19	$1,010.15	$1,010.10