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	$59.82	8.195%	$64.7222	$64.72	$64.70	$64.70
Purchase #2	$57.85	3.549%	$59.9031	$59.90	$59.90	$59.90
Purchase #3	$29.38	4.771%	$30.7817	$30.78	$30.80	$30.80
Purchase #4	$167.69	10.470%	$185.2471	$185.25	$185.25	$185.20
Purchase #5	$141.94	3.526%	$146.9448	$146.94	$146.95	$146.90
Purchase #6	$234.68	10.335%	$258.9342	$258.93	$258.95	$258.90
Purchase #7	$141.74	13.236%	$160.5007	$160.50	$160.50	$160.50
7 purchase totals =	$833.10		$907.0338	$907.02	$907.05	$906.90