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	$17.45	5.228%	$18.3623	$18.36	$18.35	$18.40
Purchase #2	$237.98	6.516%	$253.4868	$253.49	$253.50	$253.50
Purchase #3	$248.67	9.322%	$271.851	$271.85	$271.85	$271.90
Purchase #4	$147.84	6.809%	$157.9064	$157.91	$157.90	$157.90
Purchase #5	$218.85	4.146%	$227.9235	$227.92	$227.90	$227.90
Purchase #6	$63.60	12.322%	$71.4368	$71.44	$71.45	$71.40
Purchase #7	$90.85	3.821%	$94.3214	$94.32	$94.30	$94.30
7 purchase totals =	$1,025.24		$1,095.2882	$1,095.29	$1,095.25	$1,095.30