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	$77.36	6.509%	$82.3954	$82.40	$82.40	$82.40
Purchase #2	$69.99	11.777%	$78.2327	$78.23	$78.25	$78.20
Purchase #3	$169.80	11.472%	$189.2795	$189.28	$189.30	$189.30
Purchase #4	$201.81	13.269%	$228.5882	$228.59	$228.60	$228.60
Purchase #5	$214.89	6.825%	$229.5562	$229.56	$229.55	$229.60
Purchase #6	$202.88	10.858%	$224.9087	$224.91	$224.90	$224.90
Purchase #7	$166.96	5.338%	$175.8723	$175.87	$175.85	$175.90
7 purchase totals =	$1,103.69		$1,208.8330	$1,208.84	$1,208.85	$1,208.90