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	$53.89	13.639%	$61.2401	$61.24	$61.25	$61.20
Purchase #2	$243.36	4.791%	$255.0194	$255.02	$255.00	$255.00
Purchase #3	$197.33	10.712%	$218.468	$218.47	$218.45	$218.50
Purchase #4	$75.71	7.422%	$81.3292	$81.33	$81.35	$81.30
Purchase #5	$27.47	10.443%	$30.3387	$30.34	$30.35	$30.30
Purchase #6	$71.48	7.612%	$76.9211	$76.92	$76.90	$76.90
Purchase #7	$167.85	13.204%	$190.0129	$190.01	$190.00	$190.00
7 purchase totals =	$837.09		$913.3294	$913.33	$913.30	$913.20