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	$201.57	4.770%	$211.1849	$211.18	$211.20	$211.20
Purchase #2	$220.39	12.324%	$247.5509	$247.55	$247.55	$247.60
Purchase #3	$53.76	10.390%	$59.3457	$59.35	$59.35	$59.30
Purchase #4	$95.96	6.636%	$102.3279	$102.33	$102.35	$102.30
Purchase #5	$200.61	11.454%	$223.5879	$223.59	$223.60	$223.60
Purchase #6	$236.78	11.553%	$264.1352	$264.14	$264.15	$264.10
Purchase #7	$158.28	8.321%	$171.4505	$171.45	$171.45	$171.50
7 purchase totals =	$1,167.35		$1,279.5830	$1,279.59	$1,279.65	$1,279.60