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	$249.98	6.131%	$265.3063	$265.31	$265.30	$265.30
Purchase #2	$66.89	6.645%	$71.3348	$71.33	$71.35	$71.30
Purchase #3	$87.89	5.377%	$92.6158	$92.62	$92.60	$92.60
Purchase #4	$208.85	9.858%	$229.4384	$229.44	$229.45	$229.40
Purchase #5	$52.83	4.275%	$55.0885	$55.09	$55.10	$55.10
Purchase #6	$117.72	4.502%	$123.0198	$123.02	$123.00	$123.00
Purchase #7	$146.36	11.570%	$163.2939	$163.29	$163.30	$163.30
7 purchase totals =	$930.52		$1,000.0975	$1,000.10	$1,000.10	$1,000.00