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	$116.61	12.177%	$130.8096	$130.81	$130.80	$130.80
Purchase #2	$100.62	10.449%	$111.1338	$111.13	$111.15	$111.10
Purchase #3	$229.27	5.751%	$242.4553	$242.46	$242.45	$242.50
Purchase #4	$44.50	7.104%	$47.6613	$47.66	$47.65	$47.70
Purchase #5	$56.65	3.871%	$58.8429	$58.84	$58.85	$58.80
Purchase #6	$158.77	3.444%	$164.238	$164.24	$164.25	$164.20
Purchase #7	$82.78	13.402%	$93.8742	$93.87	$93.85	$93.90
7 purchase totals =	$789.20		$849.0151	$849.01	$849.00	$849.00