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	$126.86	12.280%	$142.4384	$142.44	$142.45	$142.40
Purchase #2	$47.59	9.332%	$52.0311	$52.03	$52.05	$52.00
Purchase #3	$40.36	13.439%	$45.784	$45.78	$45.80	$45.80
Purchase #4	$130.64	10.231%	$144.0058	$144.01	$144.00	$144.00
Purchase #5	$59.33	8.735%	$64.5125	$64.51	$64.50	$64.50
Purchase #6	$160.44	9.130%	$175.0882	$175.09	$175.10	$175.10
Purchase #7	$90.53	8.825%	$98.5193	$98.52	$98.50	$98.50
7 purchase totals =	$655.75		$722.3793	$722.38	$722.40	$722.30