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	$178.65	6.807%	$190.8107	$190.81	$190.80	$190.80
Purchase #2	$148.94	12.297%	$167.2552	$167.26	$167.25	$167.30
Purchase #3	$11.82	4.143%	$12.3097	$12.31	$12.30	$12.30
Purchase #4	$83.48	3.146%	$86.1063	$86.11	$86.10	$86.10
Purchase #5	$70.34	13.147%	$79.5876	$79.59	$79.60	$79.60
Purchase #6	$168.48	13.279%	$190.8525	$190.85	$190.85	$190.90
Purchase #7	$227.45	9.154%	$248.2708	$248.27	$248.25	$248.30
7 purchase totals =	$889.16		$975.1928	$975.20	$975.15	$975.30