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	$141.33	7.443%	$151.8492	$151.85	$151.85	$151.80
Purchase #2	$160.96	13.284%	$182.3419	$182.34	$182.35	$182.30
Purchase #3	$177.41	10.293%	$195.6708	$195.67	$195.65	$195.70
Purchase #4	$167.41	9.144%	$182.718	$182.72	$182.70	$182.70
Purchase #5	$162.31	5.674%	$171.5195	$171.52	$171.50	$171.50
Purchase #6	$88.99	12.130%	$99.7845	$99.78	$99.80	$99.80
Purchase #7	$161.27	6.344%	$171.501	$171.50	$171.50	$171.50
7 purchase totals =	$1,059.68		$1,155.3849	$1,155.38	$1,155.35	$1,155.30