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	$41.35	9.521%	$45.2869	$45.29	$45.30	$45.30
Purchase #2	$132.35	11.484%	$147.5491	$147.55	$147.55	$147.50
Purchase #3	$5.75	9.797%	$6.3133	$6.31	$6.30	$6.30
Purchase #4	$191.57	13.654%	$217.727	$217.73	$217.75	$217.70
Purchase #5	$33.40	6.353%	$35.5219	$35.52	$35.50	$35.50
Purchase #6	$190.29	6.583%	$202.8168	$202.82	$202.80	$202.80
Purchase #7	$78.54	13.456%	$89.1083	$89.11	$89.10	$89.10
7 purchase totals =	$673.25		$744.3233	$744.33	$744.30	$744.20