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	$40.86	5.132%	$42.9569	$42.96	$42.95	$43.00
Purchase #2	$228.74	12.110%	$256.4404	$256.44	$256.45	$256.40
Purchase #3	$30.35	11.314%	$33.7838	$33.78	$33.80	$33.80
Purchase #4	$160.35	4.715%	$167.9105	$167.91	$167.90	$167.90
Purchase #5	$92.88	12.735%	$104.7083	$104.71	$104.70	$104.70
Purchase #6	$239.38	6.596%	$255.1695	$255.17	$255.15	$255.20
Purchase #7	$78.61	13.125%	$88.9276	$88.93	$88.95	$88.90
7 purchase totals =	$871.17		$949.8970	$949.90	$949.90	$949.90