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	$136.31	7.631%	$146.7118	$146.71	$146.70	$146.70
Purchase #2	$7.60	13.247%	$8.6068	$8.61	$8.60	$8.60
Purchase #3	$110.36	12.465%	$124.1164	$124.12	$124.10	$124.10
Purchase #4	$93.97	4.843%	$98.521	$98.52	$98.50	$98.50
Purchase #5	$65.42	10.851%	$72.5187	$72.52	$72.50	$72.50
Purchase #6	$145.53	7.611%	$156.6063	$156.61	$156.60	$156.60
Purchase #7	$52.95	4.587%	$55.3788	$55.38	$55.40	$55.40
7 purchase totals =	$612.14		$662.4598	$662.47	$662.40	$662.40