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	$81.27	8.469%	$88.1528	$88.15	$88.15	$88.20
Purchase #2	$91.30	13.378%	$103.5141	$103.51	$103.50	$103.50
Purchase #3	$52.94	13.148%	$59.9006	$59.90	$59.90	$59.90
Purchase #4	$231.53	5.409%	$244.0535	$244.05	$244.05	$244.10
Purchase #5	$167.75	8.222%	$181.5424	$181.54	$181.55	$181.50
Purchase #6	$179.55	11.840%	$200.8087	$200.81	$200.80	$200.80
Purchase #7	$153.32	7.206%	$164.3682	$164.37	$164.35	$164.40
7 purchase totals =	$957.66		$1,042.3403	$1,042.33	$1,042.30	$1,042.40