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	$174.53	3.804%	$181.1691	$181.17	$181.15	$181.20
Purchase #2	$155.42	10.845%	$172.2753	$172.28	$172.30	$172.30
Purchase #3	$26.86	9.573%	$29.4313	$29.43	$29.45	$29.40
Purchase #4	$160.53	4.821%	$168.2692	$168.27	$168.25	$168.30
Purchase #5	$10.73	12.714%	$12.0942	$12.09	$12.10	$12.10
Purchase #6	$36.48	13.352%	$41.3508	$41.35	$41.35	$41.40
Purchase #7	$66.40	7.676%	$71.4969	$71.50	$71.50	$71.50
7 purchase totals =	$630.95		$676.0868	$676.09	$676.10	$676.20