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	$239.83	4.249%	$250.0204	$250.02	$250.00	$250.00
Purchase #2	$105.61	7.744%	$113.7884	$113.79	$113.80	$113.80
Purchase #3	$189.61	13.848%	$215.8672	$215.87	$215.85	$215.90
Purchase #4	$55.34	11.720%	$61.8258	$61.83	$61.85	$61.80
Purchase #5	$177.28	13.232%	$200.7377	$200.74	$200.75	$200.70
Purchase #6	$213.56	4.134%	$222.3886	$222.39	$222.40	$222.40
Purchase #7	$119.49	8.275%	$129.3778	$129.38	$129.40	$129.40
7 purchase totals =	$1,100.72		$1,194.0059	$1,194.02	$1,194.05	$1,194.00