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	$153.59	4.529%	$160.5461	$160.55	$160.55	$160.50
Purchase #2	$190.70	7.247%	$204.52	$204.52	$204.50	$204.50
Purchase #3	$40.71	12.682%	$45.8728	$45.87	$45.85	$45.90
Purchase #4	$176.82	12.444%	$198.8235	$198.82	$198.80	$198.80
Purchase #5	$218.96	8.516%	$237.6066	$237.61	$237.60	$237.60
Purchase #6	$134.90	8.740%	$146.6903	$146.69	$146.70	$146.70
Purchase #7	$220.78	8.459%	$239.4558	$239.46	$239.45	$239.50
7 purchase totals =	$1,136.46		$1,233.5151	$1,233.52	$1,233.45	$1,233.50