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	$123.53	5.585%	$130.4292	$130.43	$130.45	$130.40
Purchase #2	$221.85	7.597%	$238.7039	$238.70	$238.70	$238.70
Purchase #3	$239.86	11.596%	$267.6742	$267.67	$267.65	$267.70
Purchase #4	$156.78	9.749%	$172.0645	$172.06	$172.05	$172.10
Purchase #5	$72.86	7.525%	$78.3427	$78.34	$78.35	$78.30
Purchase #6	$245.40	4.599%	$256.6859	$256.69	$256.70	$256.70
Purchase #7	$240.30	4.269%	$250.5584	$250.56	$250.55	$250.60
7 purchase totals =	$1,300.58		$1,394.4588	$1,394.45	$1,394.45	$1,394.50