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	$178.48	7.713%	$192.2462	$192.25	$192.25	$192.20
Purchase #2	$141.91	13.650%	$161.2807	$161.28	$161.30	$161.30
Purchase #3	$177.72	4.138%	$185.0741	$185.07	$185.05	$185.10
Purchase #4	$35.33	9.146%	$38.5613	$38.56	$38.55	$38.60
Purchase #5	$31.61	13.107%	$35.7531	$35.75	$35.75	$35.80
Purchase #6	$21.86	13.829%	$24.883	$24.88	$24.90	$24.90
Purchase #7	$244.91	7.191%	$262.5215	$262.52	$262.50	$262.50
7 purchase totals =	$831.82		$900.3199	$900.31	$900.30	$900.40