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	$134.50	5.312%	$141.6446	$141.64	$141.65	$141.60
Purchase #2	$33.61	11.145%	$37.3558	$37.36	$37.35	$37.40
Purchase #3	$33.65	10.457%	$37.1688	$37.17	$37.15	$37.20
Purchase #4	$52.90	3.153%	$54.5679	$54.57	$54.55	$54.60
Purchase #5	$238.62	7.739%	$257.0868	$257.09	$257.10	$257.10
Purchase #6	$213.80	9.582%	$234.2863	$234.29	$234.30	$234.30
Purchase #7	$232.95	10.155%	$256.6061	$256.61	$256.60	$256.60
7 purchase totals =	$940.03		$1,018.7163	$1,018.73	$1,018.70	$1,018.80