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	$101.44	10.862%	$112.4584	$112.46	$112.45	$112.50
Purchase #2	$13.43	12.854%	$15.1563	$15.16	$15.15	$15.20
Purchase #3	$241.30	9.681%	$264.6603	$264.66	$264.65	$264.70
Purchase #4	$203.30	5.140%	$213.7496	$213.75	$213.75	$213.70
Purchase #5	$152.33	12.849%	$171.9029	$171.90	$171.90	$171.90
Purchase #6	$181.63	9.810%	$199.4479	$199.45	$199.45	$199.40
Purchase #7	$147.60	10.155%	$162.5888	$162.59	$162.60	$162.60
7 purchase totals =	$1,041.03		$1,139.9642	$1,139.97	$1,139.95	$1,140.00