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	$88.48	11.477%	$98.6348	$98.63	$98.65	$98.60
Purchase #2	$101.27	10.498%	$111.9013	$111.90	$111.90	$111.90
Purchase #3	$61.67	7.152%	$66.0806	$66.08	$66.10	$66.10
Purchase #4	$158.54	9.860%	$174.172	$174.17	$174.15	$174.20
Purchase #5	$244.34	11.303%	$271.9578	$271.96	$271.95	$272.00
Purchase #6	$134.67	11.155%	$149.6924	$149.69	$149.70	$149.70
Purchase #7	$189.25	10.152%	$208.4627	$208.46	$208.45	$208.50
7 purchase totals =	$978.22		$1,080.9016	$1,080.89	$1,080.90	$1,081.00