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	$147.80	3.202%	$152.5326	$152.53	$152.55	$152.50
Purchase #2	$176.73	8.517%	$191.7821	$191.78	$191.80	$191.80
Purchase #3	$129.61	6.741%	$138.347	$138.35	$138.35	$138.30
Purchase #4	$200.76	4.755%	$210.3061	$210.31	$210.30	$210.30
Purchase #5	$133.46	11.238%	$148.4582	$148.46	$148.45	$148.50
Purchase #6	$246.72	13.237%	$279.3783	$279.38	$279.40	$279.40
Purchase #7	$141.43	9.115%	$154.3213	$154.32	$154.30	$154.30
7 purchase totals =	$1,176.51		$1,275.1256	$1,275.13	$1,275.15	$1,275.10