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	$190.42	12.123%	$213.5046	$213.50	$213.50	$213.50
Purchase #2	$156.65	9.428%	$171.419	$171.42	$171.40	$171.40
Purchase #3	$237.97	9.122%	$259.6776	$259.68	$259.70	$259.70
Purchase #4	$10.76	6.615%	$11.4718	$11.47	$11.45	$11.50
Purchase #5	$138.77	8.139%	$150.0645	$150.06	$150.05	$150.10
Purchase #6	$146.27	4.482%	$152.8258	$152.83	$152.85	$152.80
Purchase #7	$179.57	3.355%	$185.5946	$185.59	$185.60	$185.60
7 purchase totals =	$1,060.41		$1,144.5579	$1,144.55	$1,144.55	$1,144.60