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	$174.33	9.441%	$190.7885	$190.79	$190.80	$190.80
Purchase #2	$210.90	8.665%	$229.1745	$229.17	$229.15	$229.20
Purchase #3	$226.39	13.302%	$256.5044	$256.50	$256.50	$256.50
Purchase #4	$100.86	8.221%	$109.1517	$109.15	$109.15	$109.20
Purchase #5	$200.64	6.421%	$213.5231	$213.52	$213.50	$213.50
Purchase #6	$51.70	3.523%	$53.5214	$53.52	$53.50	$53.50
Purchase #7	$139.62	12.220%	$156.6816	$156.68	$156.70	$156.70
7 purchase totals =	$1,104.44		$1,209.3452	$1,209.33	$1,209.30	$1,209.40