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	$9.46	7.311%	$10.1516	$10.15	$10.15	$10.20
Purchase #2	$130.72	13.651%	$148.5646	$148.56	$148.55	$148.60
Purchase #3	$55.46	13.326%	$62.8506	$62.85	$62.85	$62.90
Purchase #4	$129.90	8.713%	$141.2182	$141.22	$141.20	$141.20
Purchase #5	$137.33	4.238%	$143.15	$143.15	$143.15	$143.20
Purchase #6	$163.43	13.709%	$185.8346	$185.83	$185.85	$185.80
Purchase #7	$179.92	12.781%	$202.9156	$202.92	$202.90	$202.90
7 purchase totals =	$806.22		$894.6852	$894.68	$894.65	$894.80