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	$208.56	3.154%	$215.138	$215.14	$215.15	$215.10
Purchase #2	$224.89	4.438%	$234.8706	$234.87	$234.85	$234.90
Purchase #3	$195.71	11.602%	$218.4163	$218.42	$218.40	$218.40
Purchase #4	$83.29	3.582%	$86.2734	$86.27	$86.25	$86.30
Purchase #5	$102.69	13.615%	$116.6712	$116.67	$116.65	$116.70
Purchase #6	$234.29	9.451%	$256.4327	$256.43	$256.45	$256.40
Purchase #7	$15.93	13.351%	$18.0568	$18.06	$18.05	$18.10
7 purchase totals =	$1,065.36		$1,145.8590	$1,145.86	$1,145.80	$1,145.90