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	$202.52	10.460%	$223.7036	$223.70	$223.70	$223.70
Purchase #2	$209.38	8.778%	$227.7594	$227.76	$227.75	$227.80
Purchase #3	$74.35	11.657%	$83.017	$83.02	$83.00	$83.00
Purchase #4	$40.35	4.363%	$42.1105	$42.11	$42.10	$42.10
Purchase #5	$194.86	10.424%	$215.1722	$215.17	$215.15	$215.20
Purchase #6	$223.82	12.277%	$251.2984	$251.30	$251.30	$251.30
Purchase #7	$52.68	8.370%	$57.0893	$57.09	$57.10	$57.10
7 purchase totals =	$997.96		$1,100.1504	$1,100.15	$1,100.10	$1,100.20