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	$49.26	7.307%	$52.8594	$52.86	$52.85	$52.90
Purchase #2	$12.82	11.707%	$14.3208	$14.32	$14.30	$14.30
Purchase #3	$166.59	9.336%	$182.1428	$182.14	$182.15	$182.10
Purchase #4	$45.50	6.510%	$48.4621	$48.46	$48.45	$48.50
Purchase #5	$63.52	12.490%	$71.4536	$71.45	$71.45	$71.50
Purchase #6	$46.26	13.795%	$52.6416	$52.64	$52.65	$52.60
Purchase #7	$150.41	12.737%	$169.5677	$169.57	$169.55	$169.60
7 purchase totals =	$534.36		$591.4480	$591.44	$591.40	$591.50