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	$190.70	13.399%	$216.2519	$216.25	$216.25	$216.30
Purchase #2	$125.54	12.257%	$140.9274	$140.93	$140.95	$140.90
Purchase #3	$214.71	3.525%	$222.2785	$222.28	$222.30	$222.30
Purchase #4	$194.61	12.805%	$219.5298	$219.53	$219.55	$219.50
Purchase #5	$32.89	6.222%	$34.9364	$34.94	$34.95	$34.90
Purchase #6	$68.63	5.698%	$72.5405	$72.54	$72.55	$72.50
Purchase #7	$200.75	13.278%	$227.4056	$227.41	$227.40	$227.40
7 purchase totals =	$1,027.83		$1,133.8701	$1,133.88	$1,133.95	$1,133.80