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	$71.69	3.611%	$74.2787	$74.28	$74.30	$74.30
Purchase #2	$184.30	4.240%	$192.1143	$192.11	$192.10	$192.10
Purchase #3	$41.87	8.853%	$45.5768	$45.58	$45.60	$45.60
Purchase #4	$64.92	12.578%	$73.0856	$73.09	$73.10	$73.10
Purchase #5	$130.79	10.424%	$144.4235	$144.42	$144.40	$144.40
Purchase #6	$57.57	3.720%	$59.7116	$59.71	$59.70	$59.70
Purchase #7	$210.41	12.312%	$236.3157	$236.32	$236.30	$236.30
7 purchase totals =	$761.55		$825.5062	$825.51	$825.50	$825.50