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	$15.36	10.781%	$17.016	$17.02	$17.00	$17.00
Purchase #2	$233.27	7.689%	$251.2061	$251.21	$251.20	$251.20
Purchase #3	$96.37	3.533%	$99.7748	$99.77	$99.75	$99.80
Purchase #4	$175.93	8.135%	$190.2419	$190.24	$190.25	$190.20
Purchase #5	$208.54	3.359%	$215.5449	$215.54	$215.55	$215.50
Purchase #6	$82.88	11.254%	$92.2073	$92.21	$92.20	$92.20
Purchase #7	$138.87	8.408%	$150.5462	$150.55	$150.55	$150.50
7 purchase totals =	$951.22		$1,016.5372	$1,016.54	$1,016.50	$1,016.40