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	$196.43	11.546%	$219.1098	$219.11	$219.10	$219.10
Purchase #2	$85.54	10.208%	$94.2719	$94.27	$94.25	$94.30
Purchase #3	$73.67	8.346%	$79.8185	$79.82	$79.80	$79.80
Purchase #4	$213.48	4.557%	$223.2083	$223.21	$223.20	$223.20
Purchase #5	$13.56	12.491%	$15.2538	$15.25	$15.25	$15.30
Purchase #6	$181.95	5.858%	$192.6086	$192.61	$192.60	$192.60
Purchase #7	$83.81	6.595%	$89.3373	$89.34	$89.35	$89.30
7 purchase totals =	$848.44		$913.6082	$913.61	$913.55	$913.60