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	$204.91	7.346%	$219.9627	$219.96	$219.95	$220.00
Purchase #2	$134.81	10.439%	$148.8828	$148.88	$148.90	$148.90
Purchase #3	$60.59	6.257%	$64.3811	$64.38	$64.40	$64.40
Purchase #4	$123.78	13.429%	$140.4024	$140.40	$140.40	$140.40
Purchase #5	$171.93	6.657%	$183.3754	$183.38	$183.40	$183.40
Purchase #6	$65.81	3.218%	$67.9278	$67.93	$67.95	$67.90
Purchase #7	$159.52	12.179%	$178.9479	$178.95	$178.95	$178.90
7 purchase totals =	$921.35		$1,003.8801	$1,003.88	$1,003.95	$1,003.90