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	$117.37	12.585%	$132.141	$132.14	$132.15	$132.10
Purchase #2	$135.62	4.753%	$142.066	$142.07	$142.05	$142.10
Purchase #3	$130.99	11.861%	$146.5267	$146.53	$146.55	$146.50
Purchase #4	$36.82	6.711%	$39.291	$39.29	$39.30	$39.30
Purchase #5	$109.45	13.668%	$124.4096	$124.41	$124.40	$124.40
Purchase #6	$90.44	11.244%	$100.6091	$100.61	$100.60	$100.60
Purchase #7	$51.69	5.504%	$54.535	$54.54	$54.55	$54.50
7 purchase totals =	$672.38		$739.5784	$739.59	$739.60	$739.50