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	$124.89	9.409%	$136.6409	$136.64	$136.65	$136.60
Purchase #2	$144.53	4.587%	$151.1596	$151.16	$151.15	$151.20
Purchase #3	$169.41	3.702%	$175.6816	$175.68	$175.70	$175.70
Purchase #4	$77.35	11.267%	$86.065	$86.07	$86.05	$86.10
Purchase #5	$80.84	11.799%	$90.3783	$90.38	$90.40	$90.40
Purchase #6	$50.91	11.257%	$56.6409	$56.64	$56.65	$56.60
Purchase #7	$29.87	13.330%	$33.8517	$33.85	$33.85	$33.90
7 purchase totals =	$677.80		$730.4180	$730.42	$730.45	$730.50