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	$117.61	11.341%	$130.9482	$130.95	$130.95	$130.90
Purchase #2	$28.71	8.651%	$31.1937	$31.19	$31.20	$31.20
Purchase #3	$122.56	4.421%	$127.9784	$127.98	$128.00	$128.00
Purchase #4	$65.53	6.622%	$69.8694	$69.87	$69.85	$69.90
Purchase #5	$78.54	13.717%	$89.3133	$89.31	$89.30	$89.30
Purchase #6	$80.69	3.609%	$83.6021	$83.60	$83.60	$83.60
Purchase #7	$104.48	13.132%	$118.2003	$118.20	$118.20	$118.20
7 purchase totals =	$598.12		$651.1054	$651.10	$651.10	$651.10