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	$85.40	3.623%	$88.494	$88.49	$88.50	$88.50
Purchase #2	$208.58	10.403%	$230.2786	$230.28	$230.30	$230.30
Purchase #3	$89.48	5.361%	$94.277	$94.28	$94.30	$94.30
Purchase #4	$160.80	10.789%	$178.1487	$178.15	$178.15	$178.10
Purchase #5	$169.59	6.646%	$180.861	$180.86	$180.85	$180.90
Purchase #6	$84.75	5.778%	$89.6469	$89.65	$89.65	$89.60
Purchase #7	$132.75	7.433%	$142.6173	$142.62	$142.60	$142.60
7 purchase totals =	$931.35		$1,004.3235	$1,004.33	$1,004.35	$1,004.30