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	$41.78	9.763%	$45.859	$45.86	$45.85	$45.90
Purchase #2	$146.94	11.662%	$164.0761	$164.08	$164.10	$164.10
Purchase #3	$136.94	11.299%	$152.4129	$152.41	$152.40	$152.40
Purchase #4	$65.64	11.138%	$72.951	$72.95	$72.95	$73.00
Purchase #5	$236.71	7.134%	$253.5969	$253.60	$253.60	$253.60
Purchase #6	$175.78	8.152%	$190.1096	$190.11	$190.10	$190.10
Purchase #7	$73.99	11.178%	$82.2606	$82.26	$82.25	$82.30
7 purchase totals =	$877.78		$961.2661	$961.27	$961.25	$961.40