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	$95.43	5.364%	$100.5489	$100.55	$100.55	$100.50
Purchase #2	$68.62	6.805%	$73.2896	$73.29	$73.30	$73.30
Purchase #3	$194.28	7.364%	$208.5868	$208.59	$208.60	$208.60
Purchase #4	$209.42	3.272%	$216.2722	$216.27	$216.25	$216.30
Purchase #5	$220.55	10.278%	$243.2181	$243.22	$243.20	$243.20
Purchase #6	$73.49	12.277%	$82.5124	$82.51	$82.50	$82.50
Purchase #7	$162.37	11.352%	$180.8022	$180.80	$180.80	$180.80
7 purchase totals =	$1,024.16		$1,105.2302	$1,105.23	$1,105.20	$1,105.20