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	$125.92	3.604%	$130.4582	$130.46	$130.45	$130.50
Purchase #2	$98.30	7.777%	$105.9448	$105.94	$105.95	$105.90
Purchase #3	$247.46	11.376%	$275.611	$275.61	$275.60	$275.60
Purchase #4	$139.96	11.469%	$156.012	$156.01	$156.00	$156.00
Purchase #5	$121.79	7.119%	$130.4602	$130.46	$130.45	$130.50
Purchase #6	$112.41	5.861%	$118.9984	$119.00	$119.00	$119.00
Purchase #7	$172.51	11.210%	$191.8484	$191.85	$191.85	$191.80
7 purchase totals =	$1,018.35		$1,109.3330	$1,109.33	$1,109.30	$1,109.30