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	$239.47	9.450%	$262.0999	$262.10	$262.10	$262.10
Purchase #2	$143.89	10.745%	$159.351	$159.35	$159.35	$159.40
Purchase #3	$45.46	3.534%	$47.0666	$47.07	$47.05	$47.10
Purchase #4	$234.82	13.233%	$265.8937	$265.89	$265.90	$265.90
Purchase #5	$72.88	10.614%	$80.6155	$80.62	$80.60	$80.60
Purchase #6	$106.85	5.234%	$112.4425	$112.44	$112.45	$112.40
Purchase #7	$64.59	13.846%	$73.5331	$73.53	$73.55	$73.50
7 purchase totals =	$907.96		$1,001.0023	$1,001.00	$1,001.00	$1,001.00