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	$37.40	4.790%	$39.1915	$39.19	$39.20	$39.20
Purchase #2	$29.76	6.154%	$31.5914	$31.59	$31.60	$31.60
Purchase #3	$14.38	7.492%	$15.4573	$15.46	$15.45	$15.50
Purchase #4	$48.92	8.782%	$53.2162	$53.22	$53.20	$53.20
Purchase #5	$37.31	5.273%	$39.2774	$39.28	$39.30	$39.30
Purchase #6	$41.76	6.576%	$44.5061	$44.51	$44.50	$44.50
Purchase #7	$169.50	8.148%	$183.3109	$183.31	$183.30	$183.30
7 purchase totals =	$379.03		$406.5508	$406.56	$406.55	$406.60