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	$218.75	11.371%	$243.6241	$243.62	$243.60	$243.60
Purchase #2	$69.68	3.258%	$71.9502	$71.95	$71.95	$72.00
Purchase #3	$245.31	3.281%	$253.3586	$253.36	$253.35	$253.40
Purchase #4	$138.63	8.180%	$149.9699	$149.97	$149.95	$150.00
Purchase #5	$104.70	7.181%	$112.2185	$112.22	$112.20	$112.20
Purchase #6	$172.98	13.621%	$196.5416	$196.54	$196.55	$196.50
Purchase #7	$13.51	3.159%	$13.9368	$13.94	$13.95	$13.90
7 purchase totals =	$963.56		$1,041.5997	$1,041.60	$1,041.55	$1,041.60