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	$79.45	9.252%	$86.8007	$86.80	$86.80	$86.80
Purchase #2	$25.29	4.144%	$26.338	$26.34	$26.35	$26.30
Purchase #3	$36.60	8.711%	$39.7882	$39.79	$39.80	$39.80
Purchase #4	$169.83	12.330%	$190.77	$190.77	$190.75	$190.80
Purchase #5	$206.33	4.270%	$215.1403	$215.14	$215.15	$215.10
Purchase #6	$185.75	3.276%	$191.8352	$191.84	$191.85	$191.80
Purchase #7	$237.58	11.763%	$265.5265	$265.53	$265.55	$265.50
7 purchase totals =	$940.83		$1,016.1989	$1,016.21	$1,016.25	$1,016.10