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	$224.61	13.300%	$254.4831	$254.48	$254.50	$254.50
Purchase #2	$182.76	6.861%	$195.2992	$195.30	$195.30	$195.30
Purchase #3	$211.70	4.736%	$221.7261	$221.73	$221.75	$221.70
Purchase #4	$18.96	13.465%	$21.513	$21.51	$21.50	$21.50
Purchase #5	$56.27	6.172%	$59.743	$59.74	$59.75	$59.70
Purchase #6	$222.54	4.478%	$232.5053	$232.51	$232.50	$232.50
Purchase #7	$227.43	5.788%	$240.5936	$240.59	$240.60	$240.60
7 purchase totals =	$1,144.27		$1,225.8633	$1,225.86	$1,225.90	$1,225.80