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	$216.28	11.653%	$241.4831	$241.48	$241.50	$241.50
Purchase #2	$91.88	7.741%	$98.9924	$98.99	$99.00	$99.00
Purchase #3	$177.34	9.190%	$193.6375	$193.64	$193.65	$193.60
Purchase #4	$81.73	8.393%	$88.5896	$88.59	$88.60	$88.60
Purchase #5	$141.98	6.621%	$151.3805	$151.38	$151.40	$151.40
Purchase #6	$126.40	3.418%	$130.7204	$130.72	$130.70	$130.70
Purchase #7	$209.89	6.234%	$222.9745	$222.97	$222.95	$223.00
7 purchase totals =	$1,045.50		$1,127.7780	$1,127.77	$1,127.80	$1,127.80