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	$124.72	13.809%	$141.9426	$141.94	$141.95	$141.90
Purchase #2	$95.88	11.753%	$107.1488	$107.15	$107.15	$107.10
Purchase #3	$33.63	4.851%	$35.2614	$35.26	$35.25	$35.30
Purchase #4	$139.31	8.311%	$150.8881	$150.89	$150.90	$150.90
Purchase #5	$215.55	10.496%	$238.1741	$238.17	$238.15	$238.20
Purchase #6	$69.41	13.138%	$78.5291	$78.53	$78.55	$78.50
Purchase #7	$219.67	9.777%	$241.1471	$241.15	$241.15	$241.10
7 purchase totals =	$898.17		$993.0912	$993.09	$993.10	$993.00