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	$187.36	6.173%	$198.9257	$198.93	$198.95	$198.90
Purchase #2	$81.79	11.373%	$91.092	$91.09	$91.10	$91.10
Purchase #3	$204.89	13.371%	$232.2858	$232.29	$232.30	$232.30
Purchase #4	$151.52	13.567%	$172.0767	$172.08	$172.10	$172.10
Purchase #5	$108.39	9.201%	$118.363	$118.36	$118.35	$118.40
Purchase #6	$91.35	9.291%	$99.8373	$99.84	$99.85	$99.80
Purchase #7	$219.64	8.502%	$238.3138	$238.31	$238.30	$238.30
7 purchase totals =	$1,044.94		$1,150.8943	$1,150.90	$1,150.95	$1,150.90