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	$43.45	13.251%	$49.2076	$49.21	$49.20	$49.20
Purchase #2	$156.37	7.368%	$167.8913	$167.89	$167.90	$167.90
Purchase #3	$235.59	3.413%	$243.6307	$243.63	$243.65	$243.60
Purchase #4	$208.43	6.625%	$222.2385	$222.24	$222.25	$222.20
Purchase #5	$152.68	8.429%	$165.5494	$165.55	$165.55	$165.50
Purchase #6	$79.65	13.406%	$90.3279	$90.33	$90.35	$90.30
Purchase #7	$207.41	3.274%	$214.2006	$214.20	$214.20	$214.20
7 purchase totals =	$1,083.58		$1,153.0460	$1,153.05	$1,153.10	$1,152.90