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	$210.85	9.227%	$230.3051	$230.31	$230.30	$230.30
Purchase #2	$181.29	4.337%	$189.1525	$189.15	$189.15	$189.20
Purchase #3	$39.76	4.745%	$41.6466	$41.65	$41.65	$41.60
Purchase #4	$81.53	5.127%	$85.71	$85.71	$85.70	$85.70
Purchase #5	$92.34	8.474%	$100.1649	$100.16	$100.15	$100.20
Purchase #6	$247.95	12.526%	$279.0082	$279.01	$279.00	$279.00
Purchase #7	$102.54	8.775%	$111.5379	$111.54	$111.55	$111.50
7 purchase totals =	$956.26		$1,037.5252	$1,037.53	$1,037.50	$1,037.50