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	$136.34	7.385%	$146.4087	$146.41	$146.40	$146.40
Purchase #2	$15.73	9.327%	$17.1971	$17.20	$17.20	$17.20
Purchase #3	$80.60	11.122%	$89.5643	$89.56	$89.55	$89.60
Purchase #4	$199.86	11.241%	$222.3263	$222.33	$222.35	$222.30
Purchase #5	$20.51	8.582%	$22.2702	$22.27	$22.25	$22.30
Purchase #6	$42.66	7.487%	$45.854	$45.85	$45.85	$45.90
Purchase #7	$170.89	11.786%	$191.0311	$191.03	$191.05	$191.00
7 purchase totals =	$666.59		$734.6517	$734.65	$734.65	$734.70