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	$43.95	5.106%	$46.1941	$46.19	$46.20	$46.20
Purchase #2	$218.64	9.455%	$239.3124	$239.31	$239.30	$239.30
Purchase #3	$201.60	10.250%	$222.264	$222.26	$222.25	$222.30
Purchase #4	$81.80	12.260%	$91.8287	$91.83	$91.85	$91.80
Purchase #5	$237.63	11.628%	$265.2616	$265.26	$265.25	$265.30
Purchase #6	$88.62	12.399%	$99.608	$99.61	$99.60	$99.60
Purchase #7	$105.66	10.248%	$116.488	$116.49	$116.50	$116.50
7 purchase totals =	$977.90		$1,080.9568	$1,080.95	$1,080.95	$1,081.00