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	$141.61	11.221%	$157.5001	$157.50	$157.50	$157.50
Purchase #2	$159.44	4.291%	$166.2816	$166.28	$166.30	$166.30
Purchase #3	$126.74	3.190%	$130.783	$130.78	$130.80	$130.80
Purchase #4	$208.43	13.593%	$236.7619	$236.76	$236.75	$236.80
Purchase #5	$171.73	11.497%	$191.4738	$191.47	$191.45	$191.50
Purchase #6	$18.47	9.626%	$20.2479	$20.25	$20.25	$20.20
Purchase #7	$229.78	11.614%	$256.4666	$256.47	$256.45	$256.50
7 purchase totals =	$1,056.20		$1,159.5149	$1,159.51	$1,159.50	$1,159.60