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	$140.45	7.535%	$151.0329	$151.03	$151.05	$151.00
Purchase #2	$200.91	11.454%	$223.9222	$223.92	$223.90	$223.90
Purchase #3	$223.38	12.279%	$250.8088	$250.81	$250.80	$250.80
Purchase #4	$75.37	9.320%	$82.3945	$82.39	$82.40	$82.40
Purchase #5	$22.68	11.275%	$25.2372	$25.24	$25.25	$25.20
Purchase #6	$87.34	8.284%	$94.5752	$94.58	$94.60	$94.60
Purchase #7	$94.41	6.188%	$100.2521	$100.25	$100.25	$100.30
7 purchase totals =	$844.54		$928.2229	$928.22	$928.25	$928.20