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	$133.92	13.774%	$152.3661	$152.37	$152.35	$152.40
Purchase #2	$12.64	9.826%	$13.882	$13.88	$13.90	$13.90
Purchase #3	$154.54	6.845%	$165.1183	$165.12	$165.10	$165.10
Purchase #4	$198.57	5.169%	$208.8341	$208.83	$208.85	$208.80
Purchase #5	$145.48	11.277%	$161.8858	$161.89	$161.90	$161.90
Purchase #6	$233.69	4.524%	$244.2621	$244.26	$244.25	$244.30
Purchase #7	$122.75	3.785%	$127.3961	$127.40	$127.40	$127.40
7 purchase totals =	$1,001.59		$1,073.7445	$1,073.75	$1,073.75	$1,073.80