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	$99.44	11.559%	$110.9343	$110.93	$110.95	$110.90
Purchase #2	$69.63	12.779%	$78.528	$78.53	$78.55	$78.50
Purchase #3	$61.79	13.724%	$70.2701	$70.27	$70.25	$70.30
Purchase #4	$71.45	11.275%	$79.506	$79.51	$79.50	$79.50
Purchase #5	$215.58	5.290%	$226.9842	$226.98	$227.00	$227.00
Purchase #6	$35.68	11.786%	$39.8852	$39.89	$39.90	$39.90
Purchase #7	$203.76	5.579%	$215.1278	$215.13	$215.15	$215.10
7 purchase totals =	$757.33		$821.2356	$821.24	$821.30	$821.20