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	$162.42	3.756%	$168.5205	$168.52	$168.50	$168.50
Purchase #2	$74.57	9.874%	$81.933	$81.93	$81.95	$81.90
Purchase #3	$123.45	4.369%	$128.8435	$128.84	$128.85	$128.80
Purchase #4	$90.69	3.531%	$93.8923	$93.89	$93.90	$93.90
Purchase #5	$247.68	10.237%	$273.035	$273.04	$273.05	$273.00
Purchase #6	$191.45	10.216%	$211.0085	$211.01	$211.00	$211.00
Purchase #7	$80.45	13.227%	$91.0911	$91.09	$91.10	$91.10
7 purchase totals =	$970.71		$1,048.3239	$1,048.32	$1,048.35	$1,048.20