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	$94.30	13.764%	$107.2795	$107.28	$107.30	$107.30
Purchase #2	$173.48	11.193%	$192.8976	$192.90	$192.90	$192.90
Purchase #3	$67.85	5.412%	$71.522	$71.52	$71.50	$71.50
Purchase #4	$240.67	13.557%	$273.2976	$273.30	$273.30	$273.30
Purchase #5	$112.70	11.588%	$125.7597	$125.76	$125.75	$125.80
Purchase #6	$182.26	7.698%	$196.2904	$196.29	$196.30	$196.30
Purchase #7	$80.72	9.376%	$88.2883	$88.29	$88.30	$88.30
7 purchase totals =	$951.98		$1,055.3351	$1,055.34	$1,055.35	$1,055.40