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	$12.36	8.656%	$13.4299	$13.43	$13.45	$13.40
Purchase #2	$85.81	5.298%	$90.3562	$90.36	$90.35	$90.40
Purchase #3	$150.64	5.157%	$158.4085	$158.41	$158.40	$158.40
Purchase #4	$200.67	13.635%	$228.0314	$228.03	$228.05	$228.00
Purchase #5	$137.60	13.381%	$156.0123	$156.01	$156.00	$156.00
Purchase #6	$250.51	5.695%	$264.7765	$264.78	$264.80	$264.80
Purchase #7	$94.99	4.322%	$99.0955	$99.10	$99.10	$99.10
7 purchase totals =	$932.58		$1,010.1103	$1,010.12	$1,010.15	$1,010.10