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	$196.83	11.118%	$218.7136	$218.71	$218.70	$218.70
Purchase #2	$118.37	4.247%	$123.3972	$123.40	$123.40	$123.40
Purchase #3	$105.29	5.307%	$110.8777	$110.88	$110.90	$110.90
Purchase #4	$144.92	4.129%	$150.9037	$150.90	$150.90	$150.90
Purchase #5	$87.36	10.321%	$96.3764	$96.38	$96.40	$96.40
Purchase #6	$209.98	13.645%	$238.6318	$238.63	$238.65	$238.60
Purchase #7	$214.79	12.425%	$241.4777	$241.48	$241.50	$241.50
7 purchase totals =	$1,077.54		$1,180.3781	$1,180.38	$1,180.45	$1,180.40