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	$112.48	10.156%	$123.9035	$123.90	$123.90	$123.90
Purchase #2	$143.59	7.315%	$154.0936	$154.09	$154.10	$154.10
Purchase #3	$127.29	3.313%	$131.5071	$131.51	$131.50	$131.50
Purchase #4	$188.58	6.491%	$200.8207	$200.82	$200.80	$200.80
Purchase #5	$245.53	12.320%	$275.7793	$275.78	$275.80	$275.80
Purchase #6	$175.77	7.620%	$189.1637	$189.16	$189.15	$189.20
Purchase #7	$66.93	6.299%	$71.1459	$71.15	$71.15	$71.10
7 purchase totals =	$1,060.17		$1,146.4138	$1,146.41	$1,146.40	$1,146.40