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	$38.55	5.713%	$40.7524	$40.75	$40.75	$40.80
Purchase #2	$222.72	6.367%	$236.9006	$236.90	$236.90	$236.90
Purchase #3	$72.80	11.346%	$81.0599	$81.06	$81.05	$81.10
Purchase #4	$61.70	4.423%	$64.429	$64.43	$64.45	$64.40
Purchase #5	$179.85	4.600%	$188.1231	$188.12	$188.10	$188.10
Purchase #6	$246.37	13.257%	$279.0313	$279.03	$279.05	$279.00
Purchase #7	$119.58	9.810%	$131.3108	$131.31	$131.30	$131.30
7 purchase totals =	$941.57		$1,021.6071	$1,021.60	$1,021.60	$1,021.60