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	$200.64	7.845%	$216.3802	$216.38	$216.40	$216.40
Purchase #2	$201.97	10.335%	$222.8436	$222.84	$222.85	$222.80
Purchase #3	$79.74	12.718%	$89.8813	$89.88	$89.90	$89.90
Purchase #4	$220.48	12.193%	$247.3631	$247.36	$247.35	$247.40
Purchase #5	$17.50	13.119%	$19.7958	$19.80	$19.80	$19.80
Purchase #6	$98.33	9.561%	$107.7313	$107.73	$107.75	$107.70
Purchase #7	$184.91	3.546%	$191.4669	$191.47	$191.45	$191.50
7 purchase totals =	$1,003.57		$1,095.4622	$1,095.46	$1,095.50	$1,095.50