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	$65.46	6.752%	$69.8799	$69.88	$69.90	$69.90
Purchase #2	$178.91	7.280%	$191.9346	$191.93	$191.95	$191.90
Purchase #3	$6.50	5.584%	$6.863	$6.86	$6.85	$6.90
Purchase #4	$158.33	5.205%	$166.5711	$166.57	$166.55	$166.60
Purchase #5	$175.81	13.455%	$199.4652	$199.47	$199.45	$199.50
Purchase #6	$170.50	11.710%	$190.4656	$190.47	$190.45	$190.50
Purchase #7	$55.64	9.814%	$61.1005	$61.10	$61.10	$61.10
7 purchase totals =	$811.15		$886.2799	$886.28	$886.25	$886.40