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	$188.48	13.606%	$214.1246	$214.12	$214.10	$214.10
Purchase #2	$37.47	3.119%	$38.6387	$38.64	$38.65	$38.60
Purchase #3	$134.51	5.520%	$141.935	$141.94	$141.95	$141.90
Purchase #4	$205.91	6.461%	$219.2138	$219.21	$219.20	$219.20
Purchase #5	$47.29	9.597%	$51.8284	$51.83	$51.85	$51.80
Purchase #6	$70.40	11.349%	$78.3897	$78.39	$78.40	$78.40
Purchase #7	$124.33	13.265%	$140.8224	$140.82	$140.80	$140.80
7 purchase totals =	$808.39		$884.9526	$884.95	$884.95	$884.80