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	$46.84	13.368%	$53.1016	$53.10	$53.10	$53.10
Purchase #2	$50.97	9.589%	$55.8575	$55.86	$55.85	$55.90
Purchase #3	$144.35	6.564%	$153.8251	$153.83	$153.85	$153.80
Purchase #4	$209.66	13.848%	$238.6937	$238.69	$238.70	$238.70
Purchase #5	$229.29	6.704%	$244.6616	$244.66	$244.65	$244.70
Purchase #6	$37.94	6.535%	$40.4194	$40.42	$40.40	$40.40
Purchase #7	$246.49	11.785%	$275.5388	$275.54	$275.55	$275.50
7 purchase totals =	$965.54		$1,062.0977	$1,062.10	$1,062.10	$1,062.10