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	$165.88	11.718%	$185.3178	$185.32	$185.30	$185.30
Purchase #2	$68.31	12.818%	$77.066	$77.07	$77.05	$77.10
Purchase #3	$162.33	13.479%	$184.2105	$184.21	$184.20	$184.20
Purchase #4	$73.66	6.630%	$78.5437	$78.54	$78.55	$78.50
Purchase #5	$174.35	13.300%	$197.5386	$197.54	$197.55	$197.50
Purchase #6	$149.67	6.345%	$159.1666	$159.17	$159.15	$159.20
Purchase #7	$246.94	6.257%	$262.391	$262.39	$262.40	$262.40
7 purchase totals =	$1,041.14		$1,144.2342	$1,144.24	$1,144.20	$1,144.20