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	$227.51	7.744%	$245.1284	$245.13	$245.15	$245.10
Purchase #2	$89.41	11.129%	$99.3604	$99.36	$99.35	$99.40
Purchase #3	$90.30	5.727%	$95.4715	$95.47	$95.45	$95.50
Purchase #4	$116.53	8.745%	$126.7205	$126.72	$126.70	$126.70
Purchase #5	$37.60	7.612%	$40.4621	$40.46	$40.45	$40.50
Purchase #6	$98.89	10.593%	$109.3654	$109.37	$109.35	$109.40
Purchase #7	$235.87	9.186%	$257.537	$257.54	$257.55	$257.50
7 purchase totals =	$896.11		$974.0453	$974.05	$974.00	$974.10