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	$152.78	6.396%	$162.5518	$162.55	$162.55	$162.60
Purchase #2	$80.76	11.476%	$90.028	$90.03	$90.05	$90.00
Purchase #3	$210.98	6.873%	$225.4807	$225.48	$225.50	$225.50
Purchase #4	$223.88	4.768%	$234.5546	$234.55	$234.55	$234.60
Purchase #5	$63.83	12.808%	$72.0053	$72.01	$72.00	$72.00
Purchase #6	$211.28	4.196%	$220.1453	$220.15	$220.15	$220.10
Purchase #7	$104.46	11.412%	$116.381	$116.38	$116.40	$116.40
7 purchase totals =	$1,047.97		$1,121.1467	$1,121.15	$1,121.20	$1,121.20