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	$151.82	13.520%	$172.3461	$172.35	$172.35	$172.30
Purchase #2	$117.75	7.765%	$126.8933	$126.89	$126.90	$126.90
Purchase #3	$225.51	3.281%	$232.909	$232.91	$232.90	$232.90
Purchase #4	$120.79	13.504%	$137.1015	$137.10	$137.10	$137.10
Purchase #5	$62.88	8.447%	$68.1915	$68.19	$68.20	$68.20
Purchase #6	$192.30	11.814%	$215.0183	$215.02	$215.00	$215.00
Purchase #7	$99.66	9.677%	$109.3041	$109.30	$109.30	$109.30
7 purchase totals =	$970.71		$1,061.7638	$1,061.76	$1,061.75	$1,061.70