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	$82.30	5.669%	$86.9656	$86.97	$86.95	$87.00
Purchase #2	$89.37	11.707%	$99.8325	$99.83	$99.85	$99.80
Purchase #3	$154.29	7.825%	$166.3632	$166.36	$166.35	$166.40
Purchase #4	$98.90	10.473%	$109.2578	$109.26	$109.25	$109.30
Purchase #5	$231.70	6.512%	$246.7883	$246.79	$246.80	$246.80
Purchase #6	$89.39	12.303%	$100.3877	$100.39	$100.40	$100.40
Purchase #7	$245.41	3.747%	$254.6055	$254.61	$254.60	$254.60
7 purchase totals =	$991.36		$1,064.2006	$1,064.21	$1,064.20	$1,064.30