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	$101.31	8.324%	$109.743	$109.74	$109.75	$109.70
Purchase #2	$63.43	6.661%	$67.6551	$67.66	$67.65	$67.70
Purchase #3	$155.54	6.490%	$165.6345	$165.63	$165.65	$165.60
Purchase #4	$83.72	7.598%	$90.081	$90.08	$90.10	$90.10
Purchase #5	$222.78	3.298%	$230.1273	$230.13	$230.15	$230.10
Purchase #6	$192.90	7.773%	$207.8941	$207.89	$207.90	$207.90
Purchase #7	$211.73	4.126%	$220.466	$220.47	$220.45	$220.50
7 purchase totals =	$1,031.41		$1,091.6010	$1,091.60	$1,091.65	$1,091.60