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	$229.48	12.668%	$258.5505	$258.55	$258.55	$258.60
Purchase #2	$200.84	7.367%	$215.6359	$215.64	$215.65	$215.60
Purchase #3	$94.27	6.344%	$100.2505	$100.25	$100.25	$100.30
Purchase #4	$237.91	7.542%	$255.8532	$255.85	$255.85	$255.90
Purchase #5	$158.49	10.160%	$174.5926	$174.59	$174.60	$174.60
Purchase #6	$6.84	13.160%	$7.7401	$7.74	$7.75	$7.70
Purchase #7	$208.84	6.739%	$222.9137	$222.91	$222.90	$222.90
7 purchase totals =	$1,136.67		$1,235.5365	$1,235.53	$1,235.55	$1,235.60