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	$48.32	5.684%	$51.0665	$51.07	$51.05	$51.10
Purchase #2	$170.34	12.617%	$191.8318	$191.83	$191.85	$191.80
Purchase #3	$197.37	11.141%	$219.359	$219.36	$219.35	$219.40
Purchase #4	$115.78	13.699%	$131.6407	$131.64	$131.65	$131.60
Purchase #5	$92.36	9.794%	$101.4057	$101.41	$101.40	$101.40
Purchase #6	$243.71	12.294%	$273.6717	$273.67	$273.65	$273.70
Purchase #7	$69.64	13.398%	$78.9704	$78.97	$78.95	$79.00
7 purchase totals =	$937.52		$1,047.9458	$1,047.95	$1,047.90	$1,048.00