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	$199.74	6.637%	$212.9967	$213.00	$213.00	$213.00
Purchase #2	$52.45	13.861%	$59.7201	$59.72	$59.70	$59.70
Purchase #3	$131.72	12.870%	$148.6724	$148.67	$148.65	$148.70
Purchase #4	$7.35	7.292%	$7.886	$7.89	$7.90	$7.90
Purchase #5	$70.98	10.774%	$78.6274	$78.63	$78.65	$78.60
Purchase #6	$119.90	11.343%	$133.5003	$133.50	$133.50	$133.50
Purchase #7	$178.73	3.475%	$184.9409	$184.94	$184.95	$184.90
7 purchase totals =	$760.87		$826.3438	$826.35	$826.35	$826.30