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	$159.83	11.701%	$178.5317	$178.53	$178.55	$178.50
Purchase #2	$182.36	5.350%	$192.1163	$192.12	$192.10	$192.10
Purchase #3	$172.37	4.491%	$180.1111	$180.11	$180.10	$180.10
Purchase #4	$152.28	4.813%	$159.6092	$159.61	$159.60	$159.60
Purchase #5	$142.94	3.705%	$148.2359	$148.24	$148.25	$148.20
Purchase #6	$200.46	9.224%	$218.9504	$218.95	$218.95	$219.00
Purchase #7	$169.59	5.153%	$178.329	$178.33	$178.35	$178.30
7 purchase totals =	$1,179.83		$1,255.8836	$1,255.89	$1,255.90	$1,255.80