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	$33.87	9.304%	$37.0213	$37.02	$37.00	$37.00
Purchase #2	$177.90	10.257%	$196.1472	$196.15	$196.15	$196.10
Purchase #3	$137.88	8.124%	$149.0814	$149.08	$149.10	$149.10
Purchase #4	$137.89	12.487%	$155.1083	$155.11	$155.10	$155.10
Purchase #5	$222.83	4.572%	$233.0178	$233.02	$233.00	$233.00
Purchase #6	$84.88	13.480%	$96.3218	$96.32	$96.30	$96.30
Purchase #7	$172.90	12.308%	$194.1805	$194.18	$194.20	$194.20
7 purchase totals =	$968.15		$1,060.8783	$1,060.88	$1,060.85	$1,060.80