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	$148.91	10.831%	$165.0384	$165.04	$165.05	$165.00
Purchase #2	$16.58	13.593%	$18.8337	$18.83	$18.85	$18.80
Purchase #3	$104.60	6.842%	$111.7567	$111.76	$111.75	$111.80
Purchase #4	$22.79	12.301%	$25.5934	$25.59	$25.60	$25.60
Purchase #5	$184.97	6.208%	$196.4529	$196.45	$196.45	$196.50
Purchase #6	$214.41	6.320%	$227.9607	$227.96	$227.95	$228.00
Purchase #7	$176.94	12.851%	$199.6786	$199.68	$199.70	$199.70
7 purchase totals =	$869.20		$945.3144	$945.31	$945.35	$945.40