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	$82.34	7.567%	$88.5707	$88.57	$88.55	$88.60
Purchase #2	$63.63	5.115%	$66.8847	$66.88	$66.90	$66.90
Purchase #3	$133.44	13.768%	$151.812	$151.81	$151.80	$151.80
Purchase #4	$118.47	8.565%	$128.617	$128.62	$128.60	$128.60
Purchase #5	$202.28	10.316%	$223.1472	$223.15	$223.15	$223.10
Purchase #6	$226.29	8.293%	$245.0562	$245.06	$245.05	$245.10
Purchase #7	$34.27	12.196%	$38.4496	$38.45	$38.45	$38.40
7 purchase totals =	$860.72		$942.5374	$942.54	$942.50	$942.50