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	$149.31	11.284%	$166.1581	$166.16	$166.15	$166.20
Purchase #2	$162.48	13.576%	$184.5383	$184.54	$184.55	$184.50
Purchase #3	$97.94	13.765%	$111.4214	$111.42	$111.40	$111.40
Purchase #4	$82.65	7.866%	$89.1512	$89.15	$89.15	$89.20
Purchase #5	$134.35	13.724%	$152.7882	$152.79	$152.80	$152.80
Purchase #6	$27.73	5.822%	$29.3444	$29.34	$29.35	$29.30
Purchase #7	$168.95	9.196%	$184.4866	$184.49	$184.50	$184.50
7 purchase totals =	$823.41		$917.8882	$917.89	$917.90	$917.90