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	$89.67	7.740%	$96.6105	$96.61	$96.60	$96.60
Purchase #2	$77.88	6.218%	$82.7226	$82.72	$82.70	$82.70
Purchase #3	$32.84	4.597%	$34.3497	$34.35	$34.35	$34.30
Purchase #4	$191.52	8.833%	$208.437	$208.44	$208.45	$208.40
Purchase #5	$136.89	10.253%	$150.9253	$150.93	$150.95	$150.90
Purchase #6	$74.75	10.255%	$82.4156	$82.42	$82.40	$82.40
Purchase #7	$88.89	5.738%	$93.9905	$93.99	$94.00	$94.00
7 purchase totals =	$692.44		$749.4512	$749.46	$749.45	$749.30