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	$240.68	12.128%	$269.8697	$269.87	$269.85	$269.90
Purchase #2	$67.44	6.115%	$71.564	$71.56	$71.55	$71.60
Purchase #3	$148.72	7.711%	$160.1878	$160.19	$160.20	$160.20
Purchase #4	$33.55	10.727%	$37.1489	$37.15	$37.15	$37.10
Purchase #5	$246.84	13.325%	$279.7314	$279.73	$279.75	$279.70
Purchase #6	$162.59	10.499%	$179.6603	$179.66	$179.65	$179.70
Purchase #7	$114.35	8.143%	$123.6615	$123.66	$123.65	$123.70
7 purchase totals =	$1,014.17		$1,121.8236	$1,121.82	$1,121.80	$1,121.90