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	$240.32	3.611%	$248.998	$249.00	$249.00	$249.00
Purchase #2	$7.38	5.610%	$7.794	$7.79	$7.80	$7.80
Purchase #3	$150.32	12.122%	$168.5418	$168.54	$168.55	$168.50
Purchase #4	$47.90	12.540%	$53.9067	$53.91	$53.90	$53.90
Purchase #5	$36.26	4.184%	$37.7771	$37.78	$37.80	$37.80
Purchase #6	$91.58	3.133%	$94.4492	$94.45	$94.45	$94.40
Purchase #7	$177.83	8.589%	$193.1038	$193.10	$193.10	$193.10
7 purchase totals =	$751.59		$804.5706	$804.57	$804.60	$804.50