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	$143.41	5.321%	$151.0408	$151.04	$151.05	$151.00
Purchase #2	$63.93	5.503%	$67.4481	$67.45	$67.45	$67.40
Purchase #3	$192.66	3.322%	$199.0602	$199.06	$199.05	$199.10
Purchase #4	$152.55	10.198%	$168.107	$168.11	$168.10	$168.10
Purchase #5	$11.55	6.247%	$12.2715	$12.27	$12.25	$12.30
Purchase #6	$109.56	6.374%	$116.5434	$116.54	$116.55	$116.50
Purchase #7	$186.48	4.693%	$195.2315	$195.23	$195.25	$195.20
7 purchase totals =	$860.14		$909.7025	$909.70	$909.70	$909.60