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	$165.55	8.373%	$179.4115	$179.41	$179.40	$179.40
Purchase #2	$184.30	5.781%	$194.9544	$194.95	$194.95	$195.00
Purchase #3	$100.42	10.757%	$111.2222	$111.22	$111.20	$111.20
Purchase #4	$236.69	10.405%	$261.3176	$261.32	$261.30	$261.30
Purchase #5	$39.44	3.402%	$40.7817	$40.78	$40.80	$40.80
Purchase #6	$230.60	12.537%	$259.5103	$259.51	$259.50	$259.50
Purchase #7	$16.26	12.503%	$18.293	$18.29	$18.30	$18.30
7 purchase totals =	$973.26		$1,065.4907	$1,065.48	$1,065.45	$1,065.50