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	$243.27	9.266%	$265.8114	$265.81	$265.80	$265.80
Purchase #2	$38.44	11.764%	$42.9621	$42.96	$42.95	$43.00
Purchase #3	$201.83	10.182%	$222.3803	$222.38	$222.40	$222.40
Purchase #4	$112.69	10.816%	$124.8786	$124.88	$124.90	$124.90
Purchase #5	$210.54	11.437%	$234.6195	$234.62	$234.60	$234.60
Purchase #6	$25.31	10.826%	$28.0501	$28.05	$28.05	$28.10
Purchase #7	$234.37	3.213%	$241.9003	$241.90	$241.90	$241.90
7 purchase totals =	$1,066.45		$1,160.6023	$1,160.60	$1,160.60	$1,160.70