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	$67.65	13.175%	$76.5629	$76.56	$76.55	$76.60
Purchase #2	$214.81	8.817%	$233.7498	$233.75	$233.75	$233.70
Purchase #3	$174.69	12.231%	$196.0563	$196.06	$196.05	$196.10
Purchase #4	$61.59	8.333%	$66.7223	$66.72	$66.70	$66.70
Purchase #5	$96.84	7.453%	$104.0575	$104.06	$104.05	$104.10
Purchase #6	$161.59	11.713%	$180.517	$180.52	$180.50	$180.50
Purchase #7	$113.53	5.684%	$119.983	$119.98	$120.00	$120.00
7 purchase totals =	$890.70		$977.6488	$977.65	$977.60	$977.70