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	$25.27	4.421%	$26.3872	$26.39	$26.40	$26.40
Purchase #2	$66.73	7.131%	$71.4885	$71.49	$71.50	$71.50
Purchase #3	$127.45	11.742%	$142.4152	$142.42	$142.40	$142.40
Purchase #4	$209.60	3.274%	$216.4623	$216.46	$216.45	$216.50
Purchase #5	$160.93	11.810%	$179.9358	$179.94	$179.95	$179.90
Purchase #6	$202.93	4.302%	$211.66	$211.66	$211.65	$211.70
Purchase #7	$183.86	3.482%	$190.262	$190.26	$190.25	$190.30
7 purchase totals =	$976.77		$1,038.6110	$1,038.62	$1,038.60	$1,038.70