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	$152.78	13.114%	$172.8156	$172.82	$172.80	$172.80
Purchase #2	$15.83	8.448%	$17.1673	$17.17	$17.15	$17.20
Purchase #3	$5.25	3.111%	$5.4133	$5.41	$5.40	$5.40
Purchase #4	$79.48	12.354%	$89.299	$89.30	$89.30	$89.30
Purchase #5	$36.43	7.792%	$39.2686	$39.27	$39.25	$39.30
Purchase #6	$147.38	11.429%	$164.2241	$164.22	$164.20	$164.20
Purchase #7	$196.46	11.717%	$219.4792	$219.48	$219.50	$219.50
7 purchase totals =	$633.61		$707.6671	$707.67	$707.60	$707.70