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	$130.41	4.661%	$136.4884	$136.49	$136.50	$136.50
Purchase #2	$15.55	5.852%	$16.46	$16.46	$16.45	$16.50
Purchase #3	$17.85	3.580%	$18.489	$18.49	$18.50	$18.50
Purchase #4	$75.31	9.169%	$82.2152	$82.22	$82.20	$82.20
Purchase #5	$219.90	7.501%	$236.3947	$236.39	$236.40	$236.40
Purchase #6	$113.69	12.731%	$128.1639	$128.16	$128.15	$128.20
Purchase #7	$190.41	9.391%	$208.2914	$208.29	$208.30	$208.30
7 purchase totals =	$763.12		$826.5026	$826.50	$826.50	$826.60