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	$99.96	4.716%	$104.6741	$104.67	$104.65	$104.70
Purchase #2	$149.40	10.625%	$165.2738	$165.27	$165.25	$165.30
Purchase #3	$92.68	8.578%	$100.6301	$100.63	$100.65	$100.60
Purchase #4	$217.60	5.630%	$229.8509	$229.85	$229.85	$229.90
Purchase #5	$219.55	13.638%	$249.4922	$249.49	$249.50	$249.50
Purchase #6	$127.57	11.460%	$142.1895	$142.19	$142.20	$142.20
Purchase #7	$212.87	10.839%	$235.943	$235.94	$235.95	$235.90
7 purchase totals =	$1,119.63		$1,228.0536	$1,228.04	$1,228.05	$1,228.10