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	$238.60	6.178%	$253.3407	$253.34	$253.35	$253.30
Purchase #2	$64.42	7.829%	$69.4634	$69.46	$69.45	$69.50
Purchase #3	$179.45	6.721%	$191.5108	$191.51	$191.50	$191.50
Purchase #4	$186.57	11.516%	$208.0554	$208.06	$208.05	$208.10
Purchase #5	$81.39	12.277%	$91.3823	$91.38	$91.40	$91.40
Purchase #6	$146.83	3.754%	$152.342	$152.34	$152.35	$152.30
Purchase #7	$111.93	11.673%	$124.9956	$125.00	$125.00	$125.00
7 purchase totals =	$1,009.19		$1,091.0902	$1,091.09	$1,091.10	$1,091.10