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	$31.61	4.845%	$33.1415	$33.14	$33.15	$33.10
Purchase #2	$136.90	8.504%	$148.542	$148.54	$148.55	$148.50
Purchase #3	$164.47	3.723%	$170.5932	$170.59	$170.60	$170.60
Purchase #4	$101.56	6.332%	$107.9908	$107.99	$108.00	$108.00
Purchase #5	$172.33	11.213%	$191.6534	$191.65	$191.65	$191.70
Purchase #6	$124.27	12.163%	$139.385	$139.39	$139.40	$139.40
Purchase #7	$213.72	4.669%	$223.6986	$223.70	$223.70	$223.70
7 purchase totals =	$944.86		$1,015.0045	$1,015.00	$1,015.05	$1,015.00