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	$213.93	12.770%	$241.2489	$241.25	$241.25	$241.20
Purchase #2	$177.80	12.538%	$200.0926	$200.09	$200.10	$200.10
Purchase #3	$88.69	4.198%	$92.4132	$92.41	$92.40	$92.40
Purchase #4	$194.88	11.264%	$216.8313	$216.83	$216.85	$216.80
Purchase #5	$103.67	4.200%	$108.0241	$108.02	$108.00	$108.00
Purchase #6	$188.28	4.612%	$196.9635	$196.96	$196.95	$197.00
Purchase #7	$38.96	7.508%	$41.8851	$41.89	$41.90	$41.90
7 purchase totals =	$1,006.21		$1,097.4587	$1,097.45	$1,097.45	$1,097.40