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	$115.71	13.748%	$131.6178	$131.62	$131.60	$131.60
Purchase #2	$213.83	6.773%	$228.3127	$228.31	$228.30	$228.30
Purchase #3	$169.90	8.431%	$184.2243	$184.22	$184.20	$184.20
Purchase #4	$57.63	8.388%	$62.464	$62.46	$62.45	$62.50
Purchase #5	$192.56	10.134%	$212.074	$212.07	$212.05	$212.10
Purchase #6	$129.72	13.504%	$147.2374	$147.24	$147.25	$147.20
Purchase #7	$87.37	8.803%	$95.0612	$95.06	$95.05	$95.10
7 purchase totals =	$966.72		$1,060.9914	$1,060.98	$1,060.90	$1,061.00