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	$144.67	6.375%	$153.8927	$153.89	$153.90	$153.90
Purchase #2	$37.59	6.680%	$40.101	$40.10	$40.10	$40.10
Purchase #3	$181.96	6.162%	$193.1724	$193.17	$193.15	$193.20
Purchase #4	$201.56	6.298%	$214.2542	$214.25	$214.25	$214.30
Purchase #5	$145.71	7.351%	$156.4211	$156.42	$156.40	$156.40
Purchase #6	$153.36	7.833%	$165.3727	$165.37	$165.35	$165.40
Purchase #7	$246.83	7.185%	$264.5647	$264.56	$264.55	$264.60
7 purchase totals =	$1,111.68		$1,187.7788	$1,187.76	$1,187.70	$1,187.90