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	$172.82	13.604%	$196.3304	$196.33	$196.35	$196.30
Purchase #2	$54.47	8.853%	$59.2922	$59.29	$59.30	$59.30
Purchase #3	$160.77	7.435%	$172.7232	$172.72	$172.70	$172.70
Purchase #4	$59.77	8.654%	$64.9425	$64.94	$64.95	$64.90
Purchase #5	$164.59	9.634%	$180.4466	$180.45	$180.45	$180.40
Purchase #6	$52.81	9.283%	$57.7124	$57.71	$57.70	$57.70
Purchase #7	$40.84	10.334%	$45.0604	$45.06	$45.05	$45.10
7 purchase totals =	$706.07		$776.5077	$776.50	$776.50	$776.40