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	$169.77	6.383%	$180.6064	$180.61	$180.60	$180.60
Purchase #2	$20.46	11.808%	$22.8759	$22.88	$22.90	$22.90
Purchase #3	$160.61	9.803%	$176.3546	$176.35	$176.35	$176.40
Purchase #4	$168.76	6.502%	$179.7328	$179.73	$179.75	$179.70
Purchase #5	$41.61	9.197%	$45.4369	$45.44	$45.45	$45.40
Purchase #6	$53.66	11.405%	$59.7799	$59.78	$59.80	$59.80
Purchase #7	$247.82	12.715%	$279.3303	$279.33	$279.35	$279.30
7 purchase totals =	$862.69		$944.1168	$944.12	$944.20	$944.10