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	$162.73	6.339%	$173.0455	$173.05	$173.05	$173.00
Purchase #2	$88.33	12.814%	$99.6486	$99.65	$99.65	$99.60
Purchase #3	$160.30	6.376%	$170.5207	$170.52	$170.50	$170.50
Purchase #4	$177.33	7.667%	$190.9259	$190.93	$190.95	$190.90
Purchase #5	$170.88	4.729%	$178.9609	$178.96	$178.95	$179.00
Purchase #6	$179.88	11.242%	$200.1021	$200.10	$200.10	$200.10
Purchase #7	$30.77	12.620%	$34.6532	$34.65	$34.65	$34.70
7 purchase totals =	$970.22		$1,047.8569	$1,047.86	$1,047.85	$1,047.80