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	$104.81	4.206%	$109.2183	$109.22	$109.20	$109.20
Purchase #2	$153.52	7.819%	$165.5237	$165.52	$165.50	$165.50
Purchase #3	$108.85	3.602%	$112.7708	$112.77	$112.75	$112.80
Purchase #4	$74.87	10.506%	$82.7358	$82.74	$82.75	$82.70
Purchase #5	$228.31	13.812%	$259.8442	$259.84	$259.85	$259.80
Purchase #6	$205.82	5.573%	$217.2903	$217.29	$217.30	$217.30
Purchase #7	$112.66	4.758%	$118.0204	$118.02	$118.00	$118.00
7 purchase totals =	$988.84		$1,065.4035	$1,065.40	$1,065.35	$1,065.30