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	$131.29	12.822%	$148.124	$148.12	$148.10	$148.10
Purchase #2	$210.63	9.275%	$230.1659	$230.17	$230.15	$230.20
Purchase #3	$111.36	3.256%	$114.9859	$114.99	$115.00	$115.00
Purchase #4	$249.72	11.788%	$279.157	$279.16	$279.15	$279.20
Purchase #5	$66.84	8.486%	$72.512	$72.51	$72.50	$72.50
Purchase #6	$242.69	9.136%	$264.8622	$264.86	$264.85	$264.90
Purchase #7	$196.46	13.820%	$223.6108	$223.61	$223.60	$223.60
7 purchase totals =	$1,208.99		$1,333.4178	$1,333.42	$1,333.35	$1,333.50