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	$167.85	5.564%	$177.1892	$177.19	$177.20	$177.20
Purchase #2	$216.31	4.161%	$225.3107	$225.31	$225.30	$225.30
Purchase #3	$79.98	4.800%	$83.819	$83.82	$83.80	$83.80
Purchase #4	$65.58	10.674%	$72.58	$72.58	$72.60	$72.60
Purchase #5	$54.68	8.856%	$59.5225	$59.52	$59.50	$59.50
Purchase #6	$119.30	10.474%	$131.7955	$131.80	$131.80	$131.80
Purchase #7	$168.27	13.446%	$190.8956	$190.90	$190.90	$190.90
7 purchase totals =	$871.97		$941.1125	$941.12	$941.10	$941.10