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	$63.41	7.830%	$68.375	$68.38	$68.40	$68.40
Purchase #2	$33.28	12.656%	$37.4919	$37.49	$37.50	$37.50
Purchase #3	$150.25	8.412%	$162.889	$162.89	$162.90	$162.90
Purchase #4	$249.67	12.796%	$281.6178	$281.62	$281.60	$281.60
Purchase #5	$235.94	7.538%	$253.7252	$253.73	$253.75	$253.70
Purchase #6	$179.96	7.335%	$193.1601	$193.16	$193.15	$193.20
Purchase #7	$68.72	3.543%	$71.1547	$71.15	$71.15	$71.20
7 purchase totals =	$981.23		$1,068.4137	$1,068.42	$1,068.45	$1,068.50