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	$71.25	10.680%	$78.8595	$78.86	$78.85	$78.90
Purchase #2	$59.94	7.665%	$64.5344	$64.53	$64.55	$64.50
Purchase #3	$214.72	13.336%	$243.3551	$243.36	$243.35	$243.40
Purchase #4	$209.89	11.763%	$234.5794	$234.58	$234.60	$234.60
Purchase #5	$70.95	10.352%	$78.2947	$78.29	$78.30	$78.30
Purchase #6	$118.33	8.419%	$128.2922	$128.29	$128.30	$128.30
Purchase #7	$201.38	13.399%	$228.3629	$228.36	$228.35	$228.40
7 purchase totals =	$946.46		$1,056.2782	$1,056.27	$1,056.30	$1,056.40