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	$232.29	11.292%	$258.5202	$258.52	$258.50	$258.50
Purchase #2	$33.67	11.582%	$37.5697	$37.57	$37.55	$37.60
Purchase #3	$227.25	6.393%	$241.7781	$241.78	$241.80	$241.80
Purchase #4	$196.94	13.779%	$224.0764	$224.08	$224.10	$224.10
Purchase #5	$174.87	4.746%	$183.1693	$183.17	$183.15	$183.20
Purchase #6	$32.98	10.518%	$36.4488	$36.45	$36.45	$36.40
Purchase #7	$28.36	13.797%	$32.2728	$32.27	$32.25	$32.30
7 purchase totals =	$926.36		$1,013.8353	$1,013.84	$1,013.80	$1,013.90