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	$168.63	11.680%	$188.326	$188.33	$188.35	$188.30
Purchase #2	$231.35	3.639%	$239.7688	$239.77	$239.75	$239.80
Purchase #3	$190.46	5.475%	$200.8877	$200.89	$200.90	$200.90
Purchase #4	$139.48	11.559%	$155.6025	$155.60	$155.60	$155.60
Purchase #5	$158.84	3.623%	$164.5948	$164.59	$164.60	$164.60
Purchase #6	$179.95	7.756%	$193.9069	$193.91	$193.90	$193.90
Purchase #7	$20.25	7.478%	$21.7643	$21.76	$21.75	$21.80
7 purchase totals =	$1,088.96		$1,164.8510	$1,164.85	$1,164.85	$1,164.90