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	$138.40	13.801%	$157.5006	$157.50	$157.50	$157.50
Purchase #2	$127.77	11.726%	$142.7523	$142.75	$142.75	$142.80
Purchase #3	$104.33	9.658%	$114.4062	$114.41	$114.40	$114.40
Purchase #4	$155.99	3.468%	$161.3997	$161.40	$161.40	$161.40
Purchase #5	$234.51	9.296%	$256.31	$256.31	$256.30	$256.30
Purchase #6	$6.39	13.472%	$7.2509	$7.25	$7.25	$7.30
Purchase #7	$227.93	12.301%	$255.9677	$255.97	$255.95	$256.00
7 purchase totals =	$995.32		$1,095.5874	$1,095.59	$1,095.55	$1,095.70