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	$164.28	4.489%	$171.6545	$171.65	$171.65	$171.70
Purchase #2	$123.47	13.610%	$140.2743	$140.27	$140.25	$140.30
Purchase #3	$86.79	4.797%	$90.9533	$90.95	$90.95	$91.00
Purchase #4	$243.78	6.375%	$259.321	$259.32	$259.30	$259.30
Purchase #5	$14.47	5.263%	$15.2316	$15.23	$15.25	$15.20
Purchase #6	$107.32	13.158%	$121.4412	$121.44	$121.45	$121.40
Purchase #7	$245.97	10.770%	$272.461	$272.46	$272.45	$272.50
7 purchase totals =	$986.08		$1,071.3369	$1,071.32	$1,071.30	$1,071.40