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	$146.61	9.359%	$160.3312	$160.33	$160.35	$160.30
Purchase #2	$214.83	3.762%	$222.9119	$222.91	$222.90	$222.90
Purchase #3	$161.32	8.391%	$174.8564	$174.86	$174.85	$174.90
Purchase #4	$209.40	4.425%	$218.666	$218.67	$218.65	$218.70
Purchase #5	$151.43	8.705%	$164.612	$164.61	$164.60	$164.60
Purchase #6	$162.47	8.177%	$175.7552	$175.76	$175.75	$175.80
Purchase #7	$43.97	9.578%	$48.1814	$48.18	$48.20	$48.20
7 purchase totals =	$1,090.03		$1,165.3141	$1,165.32	$1,165.30	$1,165.40