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	$227.34	13.808%	$258.7311	$258.73	$258.75	$258.70
Purchase #2	$236.61	11.467%	$263.7421	$263.74	$263.75	$263.70
Purchase #3	$98.79	7.824%	$106.5193	$106.52	$106.50	$106.50
Purchase #4	$6.95	13.358%	$7.8784	$7.88	$7.90	$7.90
Purchase #5	$171.60	7.827%	$185.0311	$185.03	$185.05	$185.00
Purchase #6	$35.48	13.205%	$40.1651	$40.17	$40.15	$40.20
Purchase #7	$233.34	13.812%	$265.5689	$265.57	$265.55	$265.60
7 purchase totals =	$1,010.11		$1,127.6360	$1,127.64	$1,127.65	$1,127.60