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	$203.38	5.850%	$215.2777	$215.28	$215.30	$215.30
Purchase #2	$142.32	5.748%	$150.5006	$150.50	$150.50	$150.50
Purchase #3	$34.90	9.807%	$38.3226	$38.32	$38.30	$38.30
Purchase #4	$220.40	10.168%	$242.8103	$242.81	$242.80	$242.80
Purchase #5	$126.27	3.474%	$130.6566	$130.66	$130.65	$130.70
Purchase #6	$22.65	8.490%	$24.573	$24.57	$24.55	$24.60
Purchase #7	$120.59	6.386%	$128.2909	$128.29	$128.30	$128.30
7 purchase totals =	$870.51		$930.4317	$930.43	$930.40	$930.50