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	$65.90	7.587%	$70.8998	$70.90	$70.90	$70.90
Purchase #2	$157.64	6.809%	$168.3737	$168.37	$168.35	$168.40
Purchase #3	$32.70	11.413%	$36.4321	$36.43	$36.45	$36.40
Purchase #4	$175.46	6.314%	$186.5385	$186.54	$186.55	$186.50
Purchase #5	$200.81	4.517%	$209.8806	$209.88	$209.90	$209.90
Purchase #6	$159.52	5.171%	$167.7688	$167.77	$167.75	$167.80
Purchase #7	$152.66	8.843%	$166.1597	$166.16	$166.15	$166.20
7 purchase totals =	$944.69		$1,006.0532	$1,006.05	$1,006.05	$1,006.10