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	$36.57	11.470%	$40.7646	$40.76	$40.75	$40.80
Purchase #2	$178.76	10.194%	$196.9828	$196.98	$197.00	$197.00
Purchase #3	$163.47	11.731%	$182.6467	$182.65	$182.65	$182.60
Purchase #4	$210.61	12.840%	$237.6523	$237.65	$237.65	$237.70
Purchase #5	$128.29	8.711%	$139.4653	$139.47	$139.45	$139.50
Purchase #6	$243.82	13.398%	$276.487	$276.49	$276.50	$276.50
Purchase #7	$212.41	6.684%	$226.6075	$226.61	$226.60	$226.60
7 purchase totals =	$1,173.93		$1,300.6062	$1,300.61	$1,300.60	$1,300.70