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	$63.73	11.703%	$71.1883	$71.19	$71.20	$71.20
Purchase #2	$245.59	8.567%	$266.6297	$266.63	$266.65	$266.60
Purchase #3	$150.57	13.645%	$171.1153	$171.12	$171.10	$171.10
Purchase #4	$193.29	9.120%	$210.918	$210.92	$210.90	$210.90
Purchase #5	$28.95	13.415%	$32.8336	$32.83	$32.85	$32.80
Purchase #6	$124.89	13.732%	$142.0399	$142.04	$142.05	$142.00
Purchase #7	$104.56	11.643%	$116.7339	$116.73	$116.75	$116.70
7 purchase totals =	$911.58		$1,011.4587	$1,011.46	$1,011.50	$1,011.30