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	$74.84	9.526%	$81.9693	$81.97	$81.95	$82.00
Purchase #2	$144.60	5.302%	$152.2667	$152.27	$152.25	$152.30
Purchase #3	$138.26	12.180%	$155.1001	$155.10	$155.10	$155.10
Purchase #4	$243.59	4.837%	$255.3724	$255.37	$255.35	$255.40
Purchase #5	$183.25	11.836%	$204.9395	$204.94	$204.95	$204.90
Purchase #6	$140.38	7.591%	$151.0362	$151.04	$151.05	$151.00
Purchase #7	$12.78	13.334%	$14.4841	$14.48	$14.50	$14.50
7 purchase totals =	$937.70		$1,015.1683	$1,015.17	$1,015.15	$1,015.20