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	$93.94	11.544%	$104.7844	$104.78	$104.80	$104.80
Purchase #2	$220.75	12.545%	$248.4431	$248.44	$248.45	$248.40
Purchase #3	$83.65	8.538%	$90.792	$90.79	$90.80	$90.80
Purchase #4	$57.25	11.409%	$63.7817	$63.78	$63.80	$63.80
Purchase #5	$148.57	9.628%	$162.8743	$162.87	$162.85	$162.90
Purchase #6	$91.93	9.719%	$100.8647	$100.86	$100.85	$100.90
Purchase #7	$160.59	6.428%	$170.9127	$170.91	$170.90	$170.90
7 purchase totals =	$856.68		$942.4529	$942.43	$942.45	$942.50