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	$180.53	8.631%	$196.1115	$196.11	$196.10	$196.10
Purchase #2	$207.25	7.566%	$222.9305	$222.93	$222.95	$222.90
Purchase #3	$94.90	11.530%	$105.842	$105.84	$105.85	$105.80
Purchase #4	$83.91	13.579%	$95.3041	$95.30	$95.30	$95.30
Purchase #5	$31.79	10.444%	$35.1101	$35.11	$35.10	$35.10
Purchase #6	$153.71	8.440%	$166.6831	$166.68	$166.70	$166.70
Purchase #7	$92.91	13.688%	$105.6275	$105.63	$105.65	$105.60
7 purchase totals =	$845.00		$927.6088	$927.60	$927.65	$927.50