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	$32.76	13.657%	$37.234	$37.23	$37.25	$37.20
Purchase #2	$28.45	13.248%	$32.2191	$32.22	$32.20	$32.20
Purchase #3	$34.32	10.839%	$38.0399	$38.04	$38.05	$38.00
Purchase #4	$102.30	8.372%	$110.8646	$110.86	$110.85	$110.90
Purchase #5	$203.34	9.465%	$222.5861	$222.59	$222.60	$222.60
Purchase #6	$123.57	10.644%	$136.7228	$136.72	$136.70	$136.70
Purchase #7	$173.40	5.777%	$183.4173	$183.42	$183.40	$183.40
7 purchase totals =	$698.14		$761.0838	$761.08	$761.05	$761.00