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	$99.50	9.490%	$108.9426	$108.94	$108.95	$108.90
Purchase #2	$38.95	6.850%	$41.6181	$41.62	$41.60	$41.60
Purchase #3	$98.82	5.335%	$104.092	$104.09	$104.10	$104.10
Purchase #4	$243.25	10.677%	$269.2218	$269.22	$269.20	$269.20
Purchase #5	$131.39	8.646%	$142.75	$142.75	$142.75	$142.80
Purchase #6	$41.93	9.335%	$45.8442	$45.84	$45.85	$45.80
Purchase #7	$158.58	8.537%	$172.118	$172.12	$172.10	$172.10
7 purchase totals =	$812.42		$884.5867	$884.58	$884.55	$884.50