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	$110.72	11.641%	$123.6089	$123.61	$123.60	$123.60
Purchase #2	$173.51	5.714%	$183.4244	$183.42	$183.40	$183.40
Purchase #3	$73.55	12.610%	$82.8247	$82.82	$82.80	$82.80
Purchase #4	$73.41	7.150%	$78.6588	$78.66	$78.65	$78.70
Purchase #5	$206.43	13.761%	$234.8368	$234.84	$234.85	$234.80
Purchase #6	$123.74	7.219%	$132.6728	$132.67	$132.65	$132.70
Purchase #7	$202.48	8.443%	$219.5754	$219.58	$219.60	$219.60
7 purchase totals =	$963.84		$1,055.6018	$1,055.60	$1,055.55	$1,055.60