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	$148.34	13.522%	$168.3985	$168.40	$168.40	$168.40
Purchase #2	$85.71	12.172%	$96.1426	$96.14	$96.15	$96.10
Purchase #3	$182.53	8.789%	$198.5726	$198.57	$198.55	$198.60
Purchase #4	$148.55	9.391%	$162.5003	$162.50	$162.50	$162.50
Purchase #5	$29.62	9.236%	$32.3557	$32.36	$32.35	$32.40
Purchase #6	$190.45	11.181%	$211.7442	$211.74	$211.75	$211.70
Purchase #7	$29.74	10.653%	$32.9082	$32.91	$32.90	$32.90
7 purchase totals =	$814.94		$902.6221	$902.62	$902.60	$902.60