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	$197.64	4.527%	$206.5872	$206.59	$206.60	$206.60
Purchase #2	$92.60	13.297%	$104.913	$104.91	$104.90	$104.90
Purchase #3	$30.89	7.334%	$33.1555	$33.16	$33.15	$33.20
Purchase #4	$108.27	10.389%	$119.5182	$119.52	$119.50	$119.50
Purchase #5	$179.60	12.640%	$202.3014	$202.30	$202.30	$202.30
Purchase #6	$140.88	11.165%	$156.6093	$156.61	$156.60	$156.60
Purchase #7	$72.57	12.718%	$81.7995	$81.80	$81.80	$81.80
7 purchase totals =	$822.45		$904.8841	$904.89	$904.85	$904.90