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	$57.47	4.372%	$59.9826	$59.98	$60.00	$60.00
Purchase #2	$195.99	12.612%	$220.7083	$220.71	$220.70	$220.70
Purchase #3	$178.98	9.841%	$196.5934	$196.59	$196.60	$196.60
Purchase #4	$146.44	8.129%	$158.3441	$158.34	$158.35	$158.30
Purchase #5	$155.88	10.409%	$172.1055	$172.11	$172.10	$172.10
Purchase #6	$219.27	12.769%	$247.2686	$247.27	$247.25	$247.30
Purchase #7	$173.30	12.818%	$195.5136	$195.51	$195.50	$195.50
7 purchase totals =	$1,127.33		$1,250.5161	$1,250.51	$1,250.50	$1,250.50