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	$211.25	6.389%	$224.7468	$224.75	$224.75	$224.70
Purchase #2	$204.70	4.239%	$213.3772	$213.38	$213.40	$213.40
Purchase #3	$63.68	13.873%	$72.5143	$72.51	$72.50	$72.50
Purchase #4	$237.86	10.847%	$263.6607	$263.66	$263.65	$263.70
Purchase #5	$50.80	9.238%	$55.4929	$55.49	$55.50	$55.50
Purchase #6	$78.30	5.330%	$82.4734	$82.47	$82.45	$82.50
Purchase #7	$179.72	10.533%	$198.6499	$198.65	$198.65	$198.60
7 purchase totals =	$1,026.31		$1,110.9152	$1,110.91	$1,110.90	$1,110.90