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	$72.73	11.341%	$80.9783	$80.98	$81.00	$81.00
Purchase #2	$218.57	6.208%	$232.1388	$232.14	$232.15	$232.10
Purchase #3	$99.54	12.283%	$111.7665	$111.77	$111.75	$111.80
Purchase #4	$153.32	13.847%	$174.5502	$174.55	$174.55	$174.60
Purchase #5	$110.82	4.801%	$116.1405	$116.14	$116.15	$116.10
Purchase #6	$38.30	13.334%	$43.4069	$43.41	$43.40	$43.40
Purchase #7	$247.32	7.684%	$266.3241	$266.32	$266.30	$266.30
7 purchase totals =	$940.60		$1,025.3053	$1,025.31	$1,025.30	$1,025.30