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	$158.47	3.789%	$164.4744	$164.47	$164.45	$164.50
Purchase #2	$246.48	3.366%	$254.7765	$254.78	$254.80	$254.80
Purchase #3	$45.86	11.786%	$51.2651	$51.27	$51.25	$51.30
Purchase #4	$188.48	9.594%	$206.5628	$206.56	$206.55	$206.60
Purchase #5	$238.46	5.456%	$251.4704	$251.47	$251.45	$251.50
Purchase #6	$191.86	8.403%	$207.982	$207.98	$208.00	$208.00
Purchase #7	$26.82	9.215%	$29.2915	$29.29	$29.30	$29.30
7 purchase totals =	$1,096.43		$1,165.8227	$1,165.82	$1,165.80	$1,166.00