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	$169.52	10.103%	$186.6466	$186.65	$186.65	$186.60
Purchase #2	$122.42	7.555%	$131.6688	$131.67	$131.65	$131.70
Purchase #3	$64.94	9.349%	$71.0112	$71.01	$71.00	$71.00
Purchase #4	$157.74	3.126%	$162.671	$162.67	$162.65	$162.70
Purchase #5	$119.95	4.611%	$125.4809	$125.48	$125.50	$125.50
Purchase #6	$109.71	12.334%	$123.2416	$123.24	$123.25	$123.20
Purchase #7	$89.63	7.604%	$96.4455	$96.45	$96.45	$96.40
7 purchase totals =	$833.91		$897.1656	$897.17	$897.15	$897.10