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	$183.63	6.872%	$196.2491	$196.25	$196.25	$196.20
Purchase #2	$99.76	5.259%	$105.0064	$105.01	$105.00	$105.00
Purchase #3	$213.63	5.388%	$225.1404	$225.14	$225.15	$225.10
Purchase #4	$26.56	11.579%	$29.6354	$29.64	$29.65	$29.60
Purchase #5	$209.65	8.606%	$227.6925	$227.69	$227.70	$227.70
Purchase #6	$32.85	12.213%	$36.862	$36.86	$36.85	$36.90
Purchase #7	$199.72	10.580%	$220.8504	$220.85	$220.85	$220.90
7 purchase totals =	$965.80		$1,041.4362	$1,041.44	$1,041.45	$1,041.40