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	$154.81	12.127%	$173.5838	$173.58	$173.60	$173.60
Purchase #2	$185.62	13.802%	$211.2393	$211.24	$211.25	$211.20
Purchase #3	$119.99	12.713%	$135.2443	$135.24	$135.25	$135.20
Purchase #4	$233.77	11.850%	$261.4717	$261.47	$261.45	$261.50
Purchase #5	$94.41	6.324%	$100.3805	$100.38	$100.40	$100.40
Purchase #6	$89.35	11.527%	$99.6494	$99.65	$99.65	$99.60
Purchase #7	$74.35	11.556%	$82.9419	$82.94	$82.95	$82.90
7 purchase totals =	$952.30		$1,064.5109	$1,064.50	$1,064.55	$1,064.40