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	$62.71	5.147%	$65.9377	$65.94	$65.95	$65.90
Purchase #2	$56.36	5.245%	$59.3161	$59.32	$59.30	$59.30
Purchase #3	$132.90	13.468%	$150.799	$150.80	$150.80	$150.80
Purchase #4	$141.27	9.219%	$154.2937	$154.29	$154.30	$154.30
Purchase #5	$67.67	5.692%	$71.5218	$71.52	$71.50	$71.50
Purchase #6	$110.29	13.333%	$124.995	$125.00	$125.00	$125.00
Purchase #7	$246.53	6.528%	$262.6235	$262.62	$262.60	$262.60
7 purchase totals =	$817.73		$889.4868	$889.49	$889.45	$889.40