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	$28.89	5.442%	$30.4622	$30.46	$30.45	$30.50
Purchase #2	$203.62	4.855%	$213.5058	$213.51	$213.50	$213.50
Purchase #3	$75.41	3.361%	$77.9445	$77.94	$77.95	$77.90
Purchase #4	$234.85	12.798%	$264.9061	$264.91	$264.90	$264.90
Purchase #5	$12.57	7.551%	$13.5192	$13.52	$13.50	$13.50
Purchase #6	$32.45	3.142%	$33.4696	$33.47	$33.45	$33.50
Purchase #7	$61.32	9.855%	$67.3631	$67.36	$67.35	$67.40
7 purchase totals =	$649.11		$701.1705	$701.17	$701.10	$701.20