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	$131.86	13.109%	$149.1455	$149.15	$149.15	$149.10
Purchase #2	$196.37	11.427%	$218.8092	$218.81	$218.80	$218.80
Purchase #3	$191.74	6.804%	$204.786	$204.79	$204.80	$204.80
Purchase #4	$205.89	8.248%	$222.8718	$222.87	$222.85	$222.90
Purchase #5	$235.26	12.173%	$263.8982	$263.90	$263.90	$263.90
Purchase #6	$200.61	5.395%	$211.4329	$211.43	$211.45	$211.40
Purchase #7	$153.46	3.598%	$158.9815	$158.98	$159.00	$159.00
7 purchase totals =	$1,315.19		$1,429.9251	$1,429.93	$1,429.95	$1,429.90