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	$111.59	7.682%	$120.1623	$120.16	$120.15	$120.20
Purchase #2	$164.79	4.521%	$172.2402	$172.24	$172.25	$172.20
Purchase #3	$30.79	8.802%	$33.5001	$33.50	$33.50	$33.50
Purchase #4	$185.50	10.729%	$205.4023	$205.40	$205.40	$205.40
Purchase #5	$127.74	11.405%	$142.3087	$142.31	$142.30	$142.30
Purchase #6	$178.53	11.734%	$199.4787	$199.48	$199.50	$199.50
Purchase #7	$233.84	5.445%	$246.5726	$246.57	$246.55	$246.60
7 purchase totals =	$1,032.78		$1,119.6649	$1,119.66	$1,119.65	$1,119.70