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	$77.36	10.469%	$85.4588	$85.46	$85.45	$85.50
Purchase #2	$216.68	3.536%	$224.3418	$224.34	$224.35	$224.30
Purchase #3	$173.38	6.480%	$184.615	$184.62	$184.60	$184.60
Purchase #4	$191.90	13.768%	$218.3208	$218.32	$218.30	$218.30
Purchase #5	$67.53	5.804%	$71.4494	$71.45	$71.45	$71.40
Purchase #6	$65.48	6.776%	$69.9169	$69.92	$69.90	$69.90
Purchase #7	$166.77	7.601%	$179.4462	$179.45	$179.45	$179.40
7 purchase totals =	$959.10		$1,033.5489	$1,033.56	$1,033.50	$1,033.40