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	$63.80	12.208%	$71.5887	$71.59	$71.60	$71.60
Purchase #2	$223.26	8.860%	$243.0408	$243.04	$243.05	$243.00
Purchase #3	$183.58	13.207%	$207.8254	$207.83	$207.85	$207.80
Purchase #4	$245.44	4.184%	$255.7092	$255.71	$255.70	$255.70
Purchase #5	$218.35	7.123%	$233.9031	$233.90	$233.90	$233.90
Purchase #6	$94.45	12.218%	$105.9899	$105.99	$106.00	$106.00
Purchase #7	$78.85	4.591%	$82.47	$82.47	$82.45	$82.50
7 purchase totals =	$1,107.73		$1,200.5271	$1,200.53	$1,200.55	$1,200.50