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	$80.88	5.874%	$85.6309	$85.63	$85.65	$85.60
Purchase #2	$112.65	7.742%	$121.3714	$121.37	$121.35	$121.40
Purchase #3	$245.33	10.262%	$270.5058	$270.51	$270.50	$270.50
Purchase #4	$85.86	4.198%	$89.4644	$89.46	$89.45	$89.50
Purchase #5	$213.53	12.426%	$240.0632	$240.06	$240.05	$240.10
Purchase #6	$67.49	6.818%	$72.0915	$72.09	$72.10	$72.10
Purchase #7	$62.63	10.443%	$69.1705	$69.17	$69.15	$69.20
7 purchase totals =	$868.37		$948.2977	$948.29	$948.25	$948.40