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	$210.97	5.767%	$223.1366	$223.14	$223.15	$223.10
Purchase #2	$55.90	6.534%	$59.5525	$59.55	$59.55	$59.60
Purchase #3	$146.63	13.776%	$166.8297	$166.83	$166.85	$166.80
Purchase #4	$107.44	9.316%	$117.4491	$117.45	$117.45	$117.40
Purchase #5	$114.54	7.855%	$123.5371	$123.54	$123.55	$123.50
Purchase #6	$20.65	6.625%	$22.0181	$22.02	$22.00	$22.00
Purchase #7	$50.39	8.709%	$54.7785	$54.78	$54.80	$54.80
7 purchase totals =	$706.52		$767.3016	$767.31	$767.35	$767.20