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	$240.72	12.865%	$271.6886	$271.69	$271.70	$271.70
Purchase #2	$196.27	11.353%	$218.5525	$218.55	$218.55	$218.60
Purchase #3	$16.53	11.613%	$18.4496	$18.45	$18.45	$18.40
Purchase #4	$26.89	12.574%	$30.2711	$30.27	$30.25	$30.30
Purchase #5	$231.55	3.204%	$238.9689	$238.97	$238.95	$239.00
Purchase #6	$139.36	8.771%	$151.5833	$151.58	$151.60	$151.60
Purchase #7	$65.77	9.114%	$71.7643	$71.76	$71.75	$71.80
7 purchase totals =	$917.09		$1,001.2783	$1,001.27	$1,001.25	$1,001.40