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	$97.29	12.514%	$109.4649	$109.46	$109.45	$109.50
Purchase #2	$44.38	10.610%	$49.0887	$49.09	$49.10	$49.10
Purchase #3	$36.35	13.199%	$41.1478	$41.15	$41.15	$41.10
Purchase #4	$223.33	11.507%	$249.0286	$249.03	$249.05	$249.00
Purchase #5	$85.59	6.705%	$91.3288	$91.33	$91.35	$91.30
Purchase #6	$20.78	3.812%	$21.5721	$21.57	$21.55	$21.60
Purchase #7	$153.38	7.531%	$164.931	$164.93	$164.95	$164.90
7 purchase totals =	$661.10		$726.5619	$726.56	$726.60	$726.50