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	$202.63	6.703%	$216.2123	$216.21	$216.20	$216.20
Purchase #2	$32.28	4.723%	$33.8046	$33.80	$33.80	$33.80
Purchase #3	$63.95	7.782%	$68.9266	$68.93	$68.95	$68.90
Purchase #4	$53.79	11.344%	$59.8919	$59.89	$59.90	$59.90
Purchase #5	$150.45	3.221%	$155.296	$155.30	$155.30	$155.30
Purchase #6	$89.89	3.128%	$92.7018	$92.70	$92.70	$92.70
Purchase #7	$59.95	11.586%	$66.8958	$66.90	$66.90	$66.90
7 purchase totals =	$652.94		$693.7290	$693.73	$693.75	$693.70