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	$57.43	6.424%	$61.1193	$61.12	$61.10	$61.10
Purchase #2	$202.83	7.208%	$217.45	$217.45	$217.45	$217.50
Purchase #3	$203.49	3.870%	$211.3651	$211.37	$211.35	$211.40
Purchase #4	$76.73	8.442%	$83.2075	$83.21	$83.20	$83.20
Purchase #5	$147.31	13.228%	$166.7962	$166.80	$166.80	$166.80
Purchase #6	$152.76	9.721%	$167.6098	$167.61	$167.60	$167.60
Purchase #7	$106.67	8.870%	$116.1316	$116.13	$116.15	$116.10
7 purchase totals =	$947.22		$1,023.6795	$1,023.69	$1,023.65	$1,023.70