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	$171.46	11.183%	$190.6344	$190.63	$190.65	$190.60
Purchase #2	$179.85	11.357%	$200.2756	$200.28	$200.30	$200.30
Purchase #3	$223.46	8.637%	$242.7602	$242.76	$242.75	$242.80
Purchase #4	$221.90	4.382%	$231.6237	$231.62	$231.60	$231.60
Purchase #5	$84.77	11.455%	$94.4804	$94.48	$94.50	$94.50
Purchase #6	$67.80	8.777%	$73.7508	$73.75	$73.75	$73.80
Purchase #7	$37.72	13.354%	$42.7571	$42.76	$42.75	$42.80
7 purchase totals =	$986.96		$1,076.2822	$1,076.28	$1,076.30	$1,076.40