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	$88.35	12.452%	$99.3513	$99.35	$99.35	$99.40
Purchase #2	$177.41	7.585%	$190.8665	$190.87	$190.85	$190.90
Purchase #3	$170.88	11.510%	$190.5483	$190.55	$190.55	$190.50
Purchase #4	$98.76	13.292%	$111.8872	$111.89	$111.90	$111.90
Purchase #5	$192.64	13.694%	$219.0201	$219.02	$219.00	$219.00
Purchase #6	$122.88	7.269%	$131.8121	$131.81	$131.80	$131.80
Purchase #7	$235.49	7.176%	$252.3888	$252.39	$252.40	$252.40
7 purchase totals =	$1,086.41		$1,195.8743	$1,195.88	$1,195.85	$1,195.90