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	$64.97	10.198%	$71.5956	$71.60	$71.60	$71.60
Purchase #2	$29.34	11.248%	$32.6402	$32.64	$32.65	$32.60
Purchase #3	$63.84	10.780%	$70.722	$70.72	$70.70	$70.70
Purchase #4	$52.55	6.217%	$55.817	$55.82	$55.80	$55.80
Purchase #5	$227.46	12.444%	$255.7651	$255.77	$255.75	$255.80
Purchase #6	$147.34	5.126%	$154.8926	$154.89	$154.90	$154.90
Purchase #7	$214.62	10.481%	$237.1143	$237.11	$237.10	$237.10
7 purchase totals =	$800.12		$878.5468	$878.55	$878.50	$878.50