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	$168.89	10.868%	$187.245	$187.25	$187.25	$187.20
Purchase #2	$34.60	8.344%	$37.487	$37.49	$37.50	$37.50
Purchase #3	$30.46	3.354%	$31.4816	$31.48	$31.50	$31.50
Purchase #4	$82.80	12.482%	$93.1351	$93.14	$93.15	$93.10
Purchase #5	$152.39	8.693%	$165.6373	$165.64	$165.65	$165.60
Purchase #6	$124.32	3.690%	$128.9074	$128.91	$128.90	$128.90
Purchase #7	$97.76	7.205%	$104.8036	$104.80	$104.80	$104.80
7 purchase totals =	$691.22		$748.6970	$748.71	$748.75	$748.60