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	$99.69	9.812%	$109.4716	$109.47	$109.45	$109.50
Purchase #2	$172.32	4.689%	$180.4001	$180.40	$180.40	$180.40
Purchase #3	$191.48	6.407%	$203.7481	$203.75	$203.75	$203.70
Purchase #4	$238.57	11.439%	$265.86	$265.86	$265.85	$265.90
Purchase #5	$51.69	3.419%	$53.4573	$53.46	$53.45	$53.50
Purchase #6	$212.65	10.527%	$235.0357	$235.04	$235.05	$235.00
Purchase #7	$62.25	13.706%	$70.782	$70.78	$70.80	$70.80
7 purchase totals =	$1,028.65		$1,118.7548	$1,118.76	$1,118.75	$1,118.80