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	$150.55	3.772%	$156.2287	$156.23	$156.25	$156.20
Purchase #2	$207.41	11.494%	$231.2497	$231.25	$231.25	$231.20
Purchase #3	$223.47	10.780%	$247.5601	$247.56	$247.55	$247.60
Purchase #4	$235.79	8.532%	$255.9076	$255.91	$255.90	$255.90
Purchase #5	$12.77	6.773%	$13.6349	$13.63	$13.65	$13.60
Purchase #6	$237.27	10.431%	$262.0196	$262.02	$262.00	$262.00
Purchase #7	$35.53	6.619%	$37.8817	$37.88	$37.90	$37.90
7 purchase totals =	$1,102.79		$1,204.4823	$1,204.48	$1,204.50	$1,204.40