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	$13.82	5.362%	$14.561	$14.56	$14.55	$14.60
Purchase #2	$24.52	13.476%	$27.8243	$27.82	$27.80	$27.80
Purchase #3	$89.92	3.241%	$92.8343	$92.83	$92.85	$92.80
Purchase #4	$103.68	10.236%	$114.2927	$114.29	$114.30	$114.30
Purchase #5	$171.50	10.428%	$189.384	$189.38	$189.40	$189.40
Purchase #6	$68.79	13.561%	$78.1186	$78.12	$78.10	$78.10
Purchase #7	$107.66	8.197%	$116.4849	$116.48	$116.50	$116.50
7 purchase totals =	$579.89		$633.4998	$633.48	$633.50	$633.50