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	$58.75	5.343%	$61.889	$61.89	$61.90	$61.90
Purchase #2	$172.94	13.517%	$196.3163	$196.32	$196.30	$196.30
Purchase #3	$105.62	5.290%	$111.2073	$111.21	$111.20	$111.20
Purchase #4	$55.96	13.601%	$63.5711	$63.57	$63.55	$63.60
Purchase #5	$10.39	9.635%	$11.3911	$11.39	$11.40	$11.40
Purchase #6	$26.84	4.719%	$28.1066	$28.11	$28.10	$28.10
Purchase #7	$32.46	10.256%	$35.7891	$35.79	$35.80	$35.80
7 purchase totals =	$462.96		$508.2705	$508.28	$508.25	$508.30