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	$84.72	10.132%	$93.3038	$93.30	$93.30	$93.30
Purchase #2	$89.36	7.352%	$95.9297	$95.93	$95.95	$95.90
Purchase #3	$30.40	11.851%	$34.0027	$34.00	$34.00	$34.00
Purchase #4	$35.59	6.786%	$38.0051	$38.01	$38.00	$38.00
Purchase #5	$158.31	5.426%	$166.8999	$166.90	$166.90	$166.90
Purchase #6	$57.40	9.357%	$62.7709	$62.77	$62.75	$62.80
Purchase #7	$102.77	8.766%	$111.7788	$111.78	$111.80	$111.80
7 purchase totals =	$558.55		$602.6909	$602.69	$602.70	$602.70