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	$161.68	12.521%	$181.924	$181.92	$181.90	$181.90
Purchase #2	$47.34	12.351%	$53.187	$53.19	$53.20	$53.20
Purchase #3	$34.33	10.388%	$37.8962	$37.90	$37.90	$37.90
Purchase #4	$198.56	4.180%	$206.8598	$206.86	$206.85	$206.90
Purchase #5	$120.40	4.321%	$125.6025	$125.60	$125.60	$125.60
Purchase #6	$187.85	12.228%	$210.8203	$210.82	$210.80	$210.80
Purchase #7	$99.32	12.233%	$111.4698	$111.47	$111.45	$111.50
7 purchase totals =	$849.48		$927.7596	$927.76	$927.70	$927.80