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	$41.77	11.871%	$46.7285	$46.73	$46.75	$46.70
Purchase #2	$94.41	4.758%	$98.902	$98.90	$98.90	$98.90
Purchase #3	$229.94	4.858%	$241.1105	$241.11	$241.10	$241.10
Purchase #4	$157.34	6.138%	$166.9975	$167.00	$167.00	$167.00
Purchase #5	$67.87	5.356%	$71.5051	$71.51	$71.50	$71.50
Purchase #6	$177.46	9.470%	$194.2655	$194.27	$194.25	$194.30
Purchase #7	$164.69	10.684%	$182.2855	$182.29	$182.30	$182.30
7 purchase totals =	$933.48		$1,001.7946	$1,001.81	$1,001.80	$1,001.80