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	$210.61	11.144%	$234.0804	$234.08	$234.10	$234.10
Purchase #2	$100.52	3.399%	$103.9367	$103.94	$103.95	$103.90
Purchase #3	$154.38	12.379%	$173.4907	$173.49	$173.50	$173.50
Purchase #4	$94.57	5.579%	$99.8461	$99.85	$99.85	$99.80
Purchase #5	$109.96	4.339%	$114.7312	$114.73	$114.75	$114.70
Purchase #6	$198.59	5.850%	$210.2075	$210.21	$210.20	$210.20
Purchase #7	$66.51	6.412%	$70.7746	$70.77	$70.75	$70.80
7 purchase totals =	$935.14		$1,007.0672	$1,007.07	$1,007.10	$1,007.00