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	$121.73	7.713%	$131.119	$131.12	$131.10	$131.10
Purchase #2	$211.59	5.275%	$222.7514	$222.75	$222.75	$222.80
Purchase #3	$39.75	13.836%	$45.2498	$45.25	$45.25	$45.20
Purchase #4	$54.68	10.498%	$60.4203	$60.42	$60.40	$60.40
Purchase #5	$73.74	10.137%	$81.215	$81.22	$81.20	$81.20
Purchase #6	$7.38	10.528%	$8.157	$8.16	$8.15	$8.20
Purchase #7	$166.72	12.469%	$187.5083	$187.51	$187.50	$187.50
7 purchase totals =	$675.59		$736.4208	$736.43	$736.35	$736.40