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	$72.36	12.847%	$81.6561	$81.66	$81.65	$81.70
Purchase #2	$221.42	9.393%	$242.218	$242.22	$242.20	$242.20
Purchase #3	$170.88	13.851%	$194.5486	$194.55	$194.55	$194.50
Purchase #4	$94.45	11.762%	$105.5592	$105.56	$105.55	$105.60
Purchase #5	$168.38	6.634%	$179.5503	$179.55	$179.55	$179.60
Purchase #6	$159.73	7.867%	$172.296	$172.30	$172.30	$172.30
Purchase #7	$125.38	5.152%	$131.8396	$131.84	$131.85	$131.80
7 purchase totals =	$1,012.60		$1,107.6678	$1,107.68	$1,107.65	$1,107.70