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	$172.87	8.459%	$187.4931	$187.49	$187.50	$187.50
Purchase #2	$47.96	9.706%	$52.615	$52.62	$52.60	$52.60
Purchase #3	$214.71	4.306%	$223.9554	$223.96	$223.95	$224.00
Purchase #4	$232.49	6.310%	$247.1601	$247.16	$247.15	$247.20
Purchase #5	$100.50	8.761%	$109.3048	$109.30	$109.30	$109.30
Purchase #6	$89.58	3.403%	$92.6284	$92.63	$92.65	$92.60
Purchase #7	$98.71	12.580%	$111.1277	$111.13	$111.15	$111.10
7 purchase totals =	$956.82		$1,024.2845	$1,024.29	$1,024.30	$1,024.30