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	$220.67	9.720%	$242.1191	$242.12	$242.10	$242.10
Purchase #2	$185.55	3.483%	$192.0127	$192.01	$192.00	$192.00
Purchase #3	$109.31	12.809%	$123.3115	$123.31	$123.30	$123.30
Purchase #4	$13.33	6.863%	$14.2448	$14.24	$14.25	$14.20
Purchase #5	$107.65	6.841%	$115.0143	$115.01	$115.00	$115.00
Purchase #6	$173.92	8.360%	$188.4597	$188.46	$188.45	$188.50
Purchase #7	$72.92	4.856%	$76.461	$76.46	$76.45	$76.50
7 purchase totals =	$883.35		$951.6231	$951.61	$951.55	$951.60