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	$227.29	6.171%	$241.3161	$241.32	$241.30	$241.30
Purchase #2	$188.37	11.484%	$210.0024	$210.00	$210.00	$210.00
Purchase #3	$54.93	12.139%	$61.598	$61.60	$61.60	$61.60
Purchase #4	$31.93	13.654%	$36.2897	$36.29	$36.30	$36.30
Purchase #5	$162.98	3.871%	$169.289	$169.29	$169.30	$169.30
Purchase #6	$228.29	11.403%	$254.3219	$254.32	$254.30	$254.30
Purchase #7	$150.95	10.405%	$166.6563	$166.66	$166.65	$166.70
7 purchase totals =	$1,044.74		$1,139.4734	$1,139.48	$1,139.45	$1,139.50