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	$103.73	3.670%	$107.5369	$107.54	$107.55	$107.50
Purchase #2	$128.56	4.180%	$133.9338	$133.93	$133.95	$133.90
Purchase #3	$216.61	13.158%	$245.1115	$245.11	$245.10	$245.10
Purchase #4	$103.75	7.658%	$111.6952	$111.70	$111.70	$111.70
Purchase #5	$31.56	6.803%	$33.707	$33.71	$33.70	$33.70
Purchase #6	$164.49	4.673%	$172.1766	$172.18	$172.20	$172.20
Purchase #7	$17.85	4.344%	$18.6254	$18.63	$18.65	$18.60
7 purchase totals =	$766.55		$822.7864	$822.80	$822.85	$822.70