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	$157.29	7.179%	$168.5818	$168.58	$168.60	$168.60
Purchase #2	$112.99	10.593%	$124.959	$124.96	$124.95	$125.00
Purchase #3	$112.54	9.625%	$123.372	$123.37	$123.35	$123.40
Purchase #4	$81.28	5.358%	$85.635	$85.64	$85.65	$85.60
Purchase #5	$123.84	10.402%	$136.7218	$136.72	$136.70	$136.70
Purchase #6	$103.55	8.369%	$112.2161	$112.22	$112.20	$112.20
Purchase #7	$31.60	3.398%	$32.6738	$32.67	$32.65	$32.70
7 purchase totals =	$723.09		$784.1595	$784.16	$784.10	$784.20