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	$172.30	9.246%	$188.2309	$188.23	$188.25	$188.20
Purchase #2	$111.45	12.631%	$125.5272	$125.53	$125.55	$125.50
Purchase #3	$210.87	10.223%	$232.4272	$232.43	$232.45	$232.40
Purchase #4	$94.59	4.469%	$98.8172	$98.82	$98.80	$98.80
Purchase #5	$154.41	10.414%	$170.4903	$170.49	$170.50	$170.50
Purchase #6	$99.67	11.514%	$111.146	$111.15	$111.15	$111.10
Purchase #7	$118.52	10.144%	$130.5427	$130.54	$130.55	$130.50
7 purchase totals =	$961.81		$1,057.1815	$1,057.19	$1,057.25	$1,057.00