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	$61.86	4.766%	$64.8082	$64.81	$64.80	$64.80
Purchase #2	$152.85	10.316%	$168.618	$168.62	$168.60	$168.60
Purchase #3	$69.86	12.448%	$78.5562	$78.56	$78.55	$78.60
Purchase #4	$195.64	6.610%	$208.5718	$208.57	$208.55	$208.60
Purchase #5	$71.54	11.706%	$79.9145	$79.91	$79.90	$79.90
Purchase #6	$234.88	6.616%	$250.4197	$250.42	$250.40	$250.40
Purchase #7	$134.63	7.870%	$145.2254	$145.23	$145.25	$145.20
7 purchase totals =	$921.26		$996.1138	$996.12	$996.05	$996.10