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	$44.29	8.337%	$47.9825	$47.98	$48.00	$48.00
Purchase #2	$249.88	10.731%	$276.6946	$276.69	$276.70	$276.70
Purchase #3	$52.50	12.623%	$59.1271	$59.13	$59.15	$59.10
Purchase #4	$78.93	9.359%	$86.3171	$86.32	$86.30	$86.30
Purchase #5	$90.67	5.353%	$95.5236	$95.52	$95.50	$95.50
Purchase #6	$103.42	9.344%	$113.0836	$113.08	$113.10	$113.10
Purchase #7	$73.61	13.232%	$83.3501	$83.35	$83.35	$83.40
7 purchase totals =	$693.30		$762.0786	$762.07	$762.10	$762.10