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	$11.92	3.562%	$12.3446	$12.34	$12.35	$12.30
Purchase #2	$168.53	3.287%	$174.0696	$174.07	$174.05	$174.10
Purchase #3	$165.92	5.461%	$174.9809	$174.98	$175.00	$175.00
Purchase #4	$171.26	11.707%	$191.3094	$191.31	$191.30	$191.30
Purchase #5	$96.53	9.575%	$105.7727	$105.77	$105.75	$105.80
Purchase #6	$202.93	12.781%	$228.8665	$228.87	$228.85	$228.90
Purchase #7	$75.39	3.579%	$78.0882	$78.09	$78.10	$78.10
7 purchase totals =	$892.48		$965.4319	$965.43	$965.40	$965.50