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	$99.74	13.231%	$112.9366	$112.94	$112.95	$112.90
Purchase #2	$125.57	6.241%	$133.4068	$133.41	$133.40	$133.40
Purchase #3	$206.96	12.812%	$233.4757	$233.48	$233.50	$233.50
Purchase #4	$169.35	9.747%	$185.8565	$185.86	$185.85	$185.90
Purchase #5	$192.43	11.336%	$214.2439	$214.24	$214.25	$214.20
Purchase #6	$118.39	4.383%	$123.579	$123.58	$123.60	$123.60
Purchase #7	$30.34	7.459%	$32.6031	$32.60	$32.60	$32.60
7 purchase totals =	$942.78		$1,036.1016	$1,036.11	$1,036.15	$1,036.10