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	$138.25	13.847%	$157.3935	$157.39	$157.40	$157.40
Purchase #2	$136.83	11.415%	$152.4491	$152.45	$152.45	$152.40
Purchase #3	$56.40	5.865%	$59.7079	$59.71	$59.70	$59.70
Purchase #4	$60.42	11.261%	$67.2239	$67.22	$67.20	$67.20
Purchase #5	$221.38	6.175%	$235.0502	$235.05	$235.05	$235.10
Purchase #6	$35.62	7.649%	$38.3446	$38.34	$38.35	$38.30
Purchase #7	$227.94	9.816%	$250.3146	$250.31	$250.30	$250.30
7 purchase totals =	$876.84		$960.4838	$960.47	$960.45	$960.40