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	$206.71	9.398%	$226.1366	$226.14	$226.15	$226.10
Purchase #2	$10.71	4.205%	$11.1604	$11.16	$11.15	$11.20
Purchase #3	$159.98	10.340%	$176.5219	$176.52	$176.50	$176.50
Purchase #4	$151.40	9.530%	$165.8284	$165.83	$165.85	$165.80
Purchase #5	$182.53	3.147%	$188.2742	$188.27	$188.25	$188.30
Purchase #6	$128.31	6.443%	$136.577	$136.58	$136.60	$136.60
Purchase #7	$90.41	10.281%	$99.7051	$99.71	$99.70	$99.70
7 purchase totals =	$930.05		$1,004.2036	$1,004.21	$1,004.20	$1,004.20