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	$59.56	13.465%	$67.5798	$67.58	$67.60	$67.60
Purchase #2	$92.57	12.385%	$104.0348	$104.03	$104.05	$104.00
Purchase #3	$158.77	13.220%	$179.7594	$179.76	$179.75	$179.80
Purchase #4	$218.80	8.787%	$238.026	$238.03	$238.05	$238.00
Purchase #5	$239.85	13.618%	$272.5128	$272.51	$272.50	$272.50
Purchase #6	$56.39	11.463%	$62.854	$62.85	$62.85	$62.90
Purchase #7	$94.92	12.841%	$107.1087	$107.11	$107.10	$107.10
7 purchase totals =	$920.86		$1,031.8755	$1,031.87	$1,031.90	$1,031.90