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	$209.87	3.557%	$217.3351	$217.34	$217.35	$217.30
Purchase #2	$165.49	7.850%	$178.481	$178.48	$178.50	$178.50
Purchase #3	$137.32	7.665%	$147.8456	$147.85	$147.85	$147.80
Purchase #4	$152.32	9.500%	$166.7904	$166.79	$166.80	$166.80
Purchase #5	$250.40	4.362%	$261.3224	$261.32	$261.30	$261.30
Purchase #6	$102.38	13.261%	$115.9566	$115.96	$115.95	$116.00
Purchase #7	$121.95	4.642%	$127.6109	$127.61	$127.60	$127.60
7 purchase totals =	$1,139.73		$1,215.3420	$1,215.35	$1,215.35	$1,215.30