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	$184.72	13.588%	$209.8198	$209.82	$209.80	$209.80
Purchase #2	$70.99	11.116%	$78.8812	$78.88	$78.90	$78.90
Purchase #3	$198.33	11.812%	$221.7567	$221.76	$221.75	$221.80
Purchase #4	$87.66	12.478%	$98.5982	$98.60	$98.60	$98.60
Purchase #5	$77.51	6.153%	$82.2792	$82.28	$82.30	$82.30
Purchase #6	$25.91	3.635%	$26.8518	$26.85	$26.85	$26.90
Purchase #7	$246.91	3.663%	$255.9543	$255.95	$255.95	$256.00
7 purchase totals =	$892.03		$974.1412	$974.14	$974.15	$974.30