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	$230.53	10.773%	$255.365	$255.37	$255.35	$255.40
Purchase #2	$29.36	11.329%	$32.6862	$32.69	$32.70	$32.70
Purchase #3	$192.80	13.539%	$218.9032	$218.90	$218.90	$218.90
Purchase #4	$227.37	4.153%	$236.8127	$236.81	$236.80	$236.80
Purchase #5	$88.66	11.102%	$98.503	$98.50	$98.50	$98.50
Purchase #6	$205.68	4.399%	$214.7279	$214.73	$214.75	$214.70
Purchase #7	$52.71	13.549%	$59.8517	$59.85	$59.85	$59.90
7 purchase totals =	$1,027.11		$1,116.8497	$1,116.85	$1,116.85	$1,116.90