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	$68.40	5.630%	$72.2509	$72.25	$72.25	$72.30
Purchase #2	$14.25	9.657%	$15.6261	$15.63	$15.65	$15.60
Purchase #3	$182.37	9.136%	$199.0313	$199.03	$199.05	$199.00
Purchase #4	$106.60	5.752%	$112.7316	$112.73	$112.75	$112.70
Purchase #5	$63.83	13.683%	$72.5639	$72.56	$72.55	$72.60
Purchase #6	$214.34	3.531%	$221.9083	$221.91	$221.90	$221.90
Purchase #7	$51.59	10.331%	$56.9198	$56.92	$56.90	$56.90
7 purchase totals =	$701.38		$751.0319	$751.03	$751.05	$751.00