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	$51.29	7.103%	$54.9331	$54.93	$54.95	$54.90
Purchase #2	$187.40	11.128%	$208.2539	$208.25	$208.25	$208.30
Purchase #3	$37.63	3.259%	$38.8564	$38.86	$38.85	$38.90
Purchase #4	$239.95	11.576%	$267.7266	$267.73	$267.75	$267.70
Purchase #5	$130.56	12.423%	$146.7795	$146.78	$146.80	$146.80
Purchase #6	$107.33	8.575%	$116.5335	$116.53	$116.55	$116.50
Purchase #7	$101.45	7.579%	$109.1389	$109.14	$109.15	$109.10
7 purchase totals =	$855.61		$942.2219	$942.22	$942.30	$942.20