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	$118.70	10.565%	$131.2407	$131.24	$131.25	$131.20
Purchase #2	$41.44	11.506%	$46.2081	$46.21	$46.20	$46.20
Purchase #3	$209.49	6.369%	$222.8324	$222.83	$222.85	$222.80
Purchase #4	$101.77	9.413%	$111.3496	$111.35	$111.35	$111.30
Purchase #5	$137.34	13.535%	$155.929	$155.93	$155.95	$155.90
Purchase #6	$119.69	11.586%	$133.5573	$133.56	$133.55	$133.60
Purchase #7	$186.35	9.700%	$204.426	$204.43	$204.45	$204.40
7 purchase totals =	$914.78		$1,005.5431	$1,005.55	$1,005.60	$1,005.40