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	$156.72	5.142%	$164.7785	$164.78	$164.80	$164.80
Purchase #2	$202.45	4.483%	$211.5258	$211.53	$211.55	$211.50
Purchase #3	$24.77	10.521%	$27.3761	$27.38	$27.40	$27.40
Purchase #4	$16.75	10.483%	$18.5059	$18.51	$18.50	$18.50
Purchase #5	$152.33	8.633%	$165.4806	$165.48	$165.50	$165.50
Purchase #6	$142.54	4.550%	$149.0256	$149.03	$149.05	$149.00
Purchase #7	$159.52	11.630%	$178.0722	$178.07	$178.05	$178.10
7 purchase totals =	$855.08		$914.7647	$914.78	$914.85	$914.80