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	$50.80	3.282%	$52.4673	$52.47	$52.45	$52.50
Purchase #2	$35.34	9.354%	$38.6457	$38.65	$38.65	$38.60
Purchase #3	$52.72	8.753%	$57.3346	$57.33	$57.35	$57.30
Purchase #4	$40.79	3.328%	$42.1475	$42.15	$42.15	$42.10
Purchase #5	$217.80	11.831%	$243.5679	$243.57	$243.55	$243.60
Purchase #6	$47.31	10.201%	$52.1361	$52.14	$52.15	$52.10
Purchase #7	$249.29	5.231%	$262.3304	$262.33	$262.35	$262.30
7 purchase totals =	$694.05		$748.6295	$748.64	$748.65	$748.50