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	$187.84	4.647%	$196.5689	$196.57	$196.55	$196.60
Purchase #2	$113.49	3.513%	$117.4769	$117.48	$117.50	$117.50
Purchase #3	$228.67	4.335%	$238.5828	$238.58	$238.60	$238.60
Purchase #4	$69.62	12.506%	$78.3267	$78.33	$78.35	$78.30
Purchase #5	$81.75	9.699%	$89.6789	$89.68	$89.70	$89.70
Purchase #6	$41.65	9.110%	$45.4443	$45.44	$45.45	$45.40
Purchase #7	$157.28	9.147%	$171.6664	$171.67	$171.65	$171.70
7 purchase totals =	$880.30		$937.7449	$937.75	$937.80	$937.80