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	$162.47	8.534%	$176.3352	$176.34	$176.35	$176.30
Purchase #2	$159.69	10.390%	$176.2818	$176.28	$176.30	$176.30
Purchase #3	$131.30	12.463%	$147.6639	$147.66	$147.65	$147.70
Purchase #4	$61.37	3.742%	$63.6665	$63.67	$63.65	$63.70
Purchase #5	$151.45	10.848%	$167.8793	$167.88	$167.90	$167.90
Purchase #6	$86.65	4.250%	$90.3326	$90.33	$90.35	$90.30
Purchase #7	$91.39	10.364%	$100.8617	$100.86	$100.85	$100.90
7 purchase totals =	$844.32		$923.0210	$923.02	$923.05	$923.10