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	$32.62	4.695%	$34.1515	$34.15	$34.15	$34.20
Purchase #2	$136.31	13.357%	$154.5169	$154.52	$154.50	$154.50
Purchase #3	$82.46	7.303%	$88.4821	$88.48	$88.50	$88.50
Purchase #4	$200.77	7.495%	$215.8177	$215.82	$215.80	$215.80
Purchase #5	$141.25	6.781%	$150.8282	$150.83	$150.85	$150.80
Purchase #6	$177.76	8.188%	$192.315	$192.32	$192.30	$192.30
Purchase #7	$19.59	8.798%	$21.3135	$21.31	$21.30	$21.30
7 purchase totals =	$790.76		$857.4249	$857.43	$857.40	$857.40