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	$186.65	5.329%	$196.5966	$196.60	$196.60	$196.60
Purchase #2	$124.72	3.110%	$128.5988	$128.60	$128.60	$128.60
Purchase #3	$54.84	7.651%	$59.0358	$59.04	$59.05	$59.00
Purchase #4	$200.70	10.633%	$222.0404	$222.04	$222.05	$222.00
Purchase #5	$190.51	11.732%	$212.8606	$212.86	$212.85	$212.90
Purchase #6	$78.70	10.256%	$86.7715	$86.77	$86.75	$86.80
Purchase #7	$122.77	4.256%	$127.9951	$128.00	$128.00	$128.00
7 purchase totals =	$958.89		$1,033.8988	$1,033.91	$1,033.90	$1,033.90