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	$88.92	6.295%	$94.5175	$94.52	$94.50	$94.50
Purchase #2	$161.80	6.649%	$172.5581	$172.56	$172.55	$172.60
Purchase #3	$59.69	13.678%	$67.8544	$67.85	$67.85	$67.90
Purchase #4	$205.80	5.256%	$216.6168	$216.62	$216.60	$216.60
Purchase #5	$93.52	3.790%	$97.0644	$97.06	$97.05	$97.10
Purchase #6	$95.50	11.592%	$106.5704	$106.57	$106.55	$106.60
Purchase #7	$137.37	3.750%	$142.5214	$142.52	$142.50	$142.50
7 purchase totals =	$842.60		$897.7030	$897.70	$897.60	$897.80