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	$196.59	12.287%	$220.745	$220.75	$220.75	$220.70
Purchase #2	$167.32	10.474%	$184.8451	$184.85	$184.85	$184.80
Purchase #3	$119.65	3.275%	$123.5685	$123.57	$123.55	$123.60
Purchase #4	$28.46	12.815%	$32.1071	$32.11	$32.10	$32.10
Purchase #5	$248.96	5.838%	$263.4943	$263.49	$263.50	$263.50
Purchase #6	$134.78	13.110%	$152.4497	$152.45	$152.45	$152.40
Purchase #7	$78.48	4.203%	$81.7785	$81.78	$81.80	$81.80
7 purchase totals =	$974.24		$1,058.9882	$1,059.00	$1,059.00	$1,058.90