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	$231.91	13.313%	$262.7842	$262.78	$262.80	$262.80
Purchase #2	$38.86	11.706%	$43.409	$43.41	$43.40	$43.40
Purchase #3	$214.82	3.127%	$221.5374	$221.54	$221.55	$221.50
Purchase #4	$43.53	3.356%	$44.9909	$44.99	$45.00	$45.00
Purchase #5	$93.50	12.742%	$105.4138	$105.41	$105.40	$105.40
Purchase #6	$158.62	4.354%	$165.5263	$165.53	$165.55	$165.50
Purchase #7	$196.59	3.515%	$203.5001	$203.50	$203.50	$203.50
7 purchase totals =	$977.83		$1,047.1617	$1,047.16	$1,047.20	$1,047.10