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	$156.55	10.468%	$172.9377	$172.94	$172.95	$172.90
Purchase #2	$195.44	11.752%	$218.4081	$218.41	$218.40	$218.40
Purchase #3	$66.31	9.738%	$72.7673	$72.77	$72.75	$72.80
Purchase #4	$119.69	5.358%	$126.103	$126.10	$126.10	$126.10
Purchase #5	$77.66	3.863%	$80.66	$80.66	$80.65	$80.70
Purchase #6	$96.67	3.147%	$99.7122	$99.71	$99.70	$99.70
Purchase #7	$230.70	3.519%	$238.8183	$238.82	$238.80	$238.80
7 purchase totals =	$943.02		$1,009.4066	$1,009.41	$1,009.35	$1,009.40