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	$236.49	11.459%	$263.5894	$263.59	$263.60	$263.60
Purchase #2	$185.85	13.610%	$211.1442	$211.14	$211.15	$211.10
Purchase #3	$102.90	8.423%	$111.5673	$111.57	$111.55	$111.60
Purchase #4	$35.34	6.208%	$37.5339	$37.53	$37.55	$37.50
Purchase #5	$250.61	10.296%	$276.4128	$276.41	$276.40	$276.40
Purchase #6	$218.94	9.735%	$240.2538	$240.25	$240.25	$240.30
Purchase #7	$194.82	13.143%	$220.4252	$220.43	$220.45	$220.40
7 purchase totals =	$1,224.95		$1,360.9266	$1,360.92	$1,360.95	$1,360.90