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	$212.61	4.678%	$222.5559	$222.56	$222.55	$222.60
Purchase #2	$46.53	8.355%	$50.4176	$50.42	$50.40	$50.40
Purchase #3	$149.48	10.160%	$164.6672	$164.67	$164.65	$164.70
Purchase #4	$190.77	13.752%	$217.0047	$217.00	$217.00	$217.00
Purchase #5	$117.26	13.664%	$133.2824	$133.28	$133.30	$133.30
Purchase #6	$101.97	4.549%	$106.6086	$106.61	$106.60	$106.60
Purchase #7	$166.86	11.389%	$185.8637	$185.86	$185.85	$185.90
7 purchase totals =	$985.48		$1,080.4001	$1,080.40	$1,080.35	$1,080.50