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	$62.25	13.809%	$70.8461	$70.85	$70.85	$70.80
Purchase #2	$164.95	6.594%	$175.8268	$175.83	$175.85	$175.80
Purchase #3	$52.39	9.872%	$57.5619	$57.56	$57.55	$57.60
Purchase #4	$104.66	11.287%	$116.473	$116.47	$116.45	$116.50
Purchase #5	$96.49	5.633%	$101.9253	$101.93	$101.95	$101.90
Purchase #6	$245.56	4.259%	$256.0184	$256.02	$256.00	$256.00
Purchase #7	$35.99	3.519%	$37.2565	$37.26	$37.25	$37.30
7 purchase totals =	$762.29		$815.9080	$815.92	$815.90	$815.90