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	$228.85	6.122%	$242.8602	$242.86	$242.85	$242.90
Purchase #2	$201.90	8.283%	$218.6234	$218.62	$218.60	$218.60
Purchase #3	$56.49	13.634%	$64.1918	$64.19	$64.20	$64.20
Purchase #4	$70.70	6.521%	$75.3103	$75.31	$75.30	$75.30
Purchase #5	$109.29	12.616%	$123.078	$123.08	$123.10	$123.10
Purchase #6	$99.70	11.672%	$111.337	$111.34	$111.35	$111.30
Purchase #7	$175.91	11.736%	$196.5548	$196.55	$196.55	$196.60
7 purchase totals =	$942.84		$1,031.9555	$1,031.95	$1,031.95	$1,032.00