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	$63.43	13.824%	$72.1986	$72.20	$72.20	$72.20
Purchase #2	$147.62	10.325%	$162.8618	$162.86	$162.85	$162.90
Purchase #3	$99.46	12.490%	$111.8826	$111.88	$111.90	$111.90
Purchase #4	$206.48	6.268%	$219.4222	$219.42	$219.40	$219.40
Purchase #5	$40.66	6.212%	$43.1858	$43.19	$43.20	$43.20
Purchase #6	$179.88	10.389%	$198.5677	$198.57	$198.55	$198.60
Purchase #7	$83.48	7.638%	$89.8562	$89.86	$89.85	$89.90
7 purchase totals =	$821.01		$897.9749	$897.98	$897.95	$898.10