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	$114.39	12.251%	$128.4039	$128.40	$128.40	$128.40
Purchase #2	$232.76	3.513%	$240.9369	$240.94	$240.95	$240.90
Purchase #3	$22.91	4.474%	$23.935	$23.94	$23.95	$23.90
Purchase #4	$68.64	3.811%	$71.2559	$71.26	$71.25	$71.30
Purchase #5	$210.58	8.228%	$227.9065	$227.91	$227.90	$227.90
Purchase #6	$109.65	3.143%	$113.0963	$113.10	$113.10	$113.10
Purchase #7	$233.59	9.724%	$256.3043	$256.30	$256.30	$256.30
7 purchase totals =	$992.52		$1,061.8388	$1,061.85	$1,061.85	$1,061.80