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	$176.35	4.554%	$184.381	$184.38	$184.40	$184.40
Purchase #2	$56.70	10.806%	$62.827	$62.83	$62.85	$62.80
Purchase #3	$208.44	13.169%	$235.8895	$235.89	$235.90	$235.90
Purchase #4	$120.31	5.488%	$126.9126	$126.91	$126.90	$126.90
Purchase #5	$105.99	3.792%	$110.0091	$110.01	$110.00	$110.00
Purchase #6	$33.78	12.253%	$37.9191	$37.92	$37.90	$37.90
Purchase #7	$94.38	6.356%	$100.3788	$100.38	$100.40	$100.40
7 purchase totals =	$795.95		$858.3171	$858.32	$858.35	$858.30