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	$82.25	8.629%	$89.3474	$89.35	$89.35	$89.30
Purchase #2	$237.59	5.540%	$250.7525	$250.75	$250.75	$250.80
Purchase #3	$246.64	13.260%	$279.3445	$279.34	$279.35	$279.30
Purchase #4	$28.82	3.803%	$29.916	$29.92	$29.90	$29.90
Purchase #5	$191.25	7.772%	$206.114	$206.11	$206.10	$206.10
Purchase #6	$82.96	5.577%	$87.5867	$87.59	$87.60	$87.60
Purchase #7	$102.60	9.321%	$112.1633	$112.16	$112.15	$112.20
7 purchase totals =	$972.11		$1,055.2244	$1,055.22	$1,055.20	$1,055.20