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	$58.71	13.432%	$66.5959	$66.60	$66.60	$66.60
Purchase #2	$139.34	4.407%	$145.4807	$145.48	$145.50	$145.50
Purchase #3	$172.59	7.224%	$185.0579	$185.06	$185.05	$185.10
Purchase #4	$179.84	9.422%	$196.7845	$196.78	$196.80	$196.80
Purchase #5	$246.48	7.264%	$264.3843	$264.38	$264.40	$264.40
Purchase #6	$153.27	4.248%	$159.7809	$159.78	$159.80	$159.80
Purchase #7	$28.97	6.661%	$30.8997	$30.90	$30.90	$30.90
7 purchase totals =	$979.20		$1,048.9839	$1,048.98	$1,049.05	$1,049.10