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	$168.62	9.561%	$184.7418	$184.74	$184.75	$184.70
Purchase #2	$46.25	9.449%	$50.6202	$50.62	$50.60	$50.60
Purchase #3	$115.99	9.767%	$127.3187	$127.32	$127.30	$127.30
Purchase #4	$240.40	12.612%	$270.7192	$270.72	$270.70	$270.70
Purchase #5	$37.55	8.281%	$40.6595	$40.66	$40.65	$40.70
Purchase #6	$205.36	8.359%	$222.526	$222.53	$222.55	$222.50
Purchase #7	$88.85	12.716%	$100.1482	$100.15	$100.15	$100.10
7 purchase totals =	$903.02		$996.7336	$996.74	$996.70	$996.60