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	$76.53	11.776%	$85.5422	$85.54	$85.55	$85.50
Purchase #2	$69.47	4.777%	$72.7886	$72.79	$72.80	$72.80
Purchase #3	$206.71	7.604%	$222.4282	$222.43	$222.45	$222.40
Purchase #4	$136.27	4.478%	$142.3722	$142.37	$142.35	$142.40
Purchase #5	$152.95	7.428%	$164.3111	$164.31	$164.30	$164.30
Purchase #6	$204.71	11.339%	$227.9221	$227.92	$227.90	$227.90
Purchase #7	$140.92	6.406%	$149.9473	$149.95	$149.95	$149.90
7 purchase totals =	$987.56		$1,065.3117	$1,065.31	$1,065.30	$1,065.20