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	$180.39	5.853%	$190.9482	$190.95	$190.95	$190.90
Purchase #2	$197.93	4.222%	$206.2866	$206.29	$206.30	$206.30
Purchase #3	$198.32	6.581%	$211.3714	$211.37	$211.35	$211.40
Purchase #4	$135.90	10.633%	$150.3502	$150.35	$150.35	$150.40
Purchase #5	$128.61	10.870%	$142.5899	$142.59	$142.60	$142.60
Purchase #6	$133.89	11.304%	$149.0249	$149.02	$149.00	$149.00
Purchase #7	$189.88	5.826%	$200.9424	$200.94	$200.95	$200.90
7 purchase totals =	$1,164.92		$1,251.5136	$1,251.51	$1,251.50	$1,251.50