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	$64.75	11.799%	$72.3899	$72.39	$72.40	$72.40
Purchase #2	$183.45	10.778%	$203.2222	$203.22	$203.20	$203.20
Purchase #3	$16.73	10.721%	$18.5236	$18.52	$18.50	$18.50
Purchase #4	$89.37	13.578%	$101.5047	$101.50	$101.50	$101.50
Purchase #5	$71.49	11.398%	$79.6384	$79.64	$79.65	$79.60
Purchase #6	$156.39	3.259%	$161.4868	$161.49	$161.50	$161.50
Purchase #7	$76.60	9.468%	$83.8525	$83.85	$83.85	$83.90
7 purchase totals =	$658.78		$720.6181	$720.61	$720.60	$720.60