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	$236.39	3.409%	$244.4485	$244.45	$244.45	$244.40
Purchase #2	$121.93	12.554%	$137.2371	$137.24	$137.25	$137.20
Purchase #3	$54.63	3.646%	$56.6218	$56.62	$56.60	$56.60
Purchase #4	$194.83	6.135%	$206.7828	$206.78	$206.80	$206.80
Purchase #5	$65.93	4.264%	$68.7413	$68.74	$68.75	$68.70
Purchase #6	$225.29	8.122%	$243.5881	$243.59	$243.60	$243.60
Purchase #7	$80.82	10.333%	$89.1711	$89.17	$89.15	$89.20
7 purchase totals =	$979.82		$1,046.5907	$1,046.59	$1,046.60	$1,046.50