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	$35.62	4.157%	$37.1007	$37.10	$37.10	$37.10
Purchase #2	$82.95	6.731%	$88.5334	$88.53	$88.55	$88.50
Purchase #3	$221.86	12.289%	$249.1244	$249.12	$249.10	$249.10
Purchase #4	$152.25	12.491%	$171.2675	$171.27	$171.25	$171.30
Purchase #5	$222.75	8.248%	$241.1224	$241.12	$241.10	$241.10
Purchase #6	$156.59	12.404%	$176.0134	$176.01	$176.00	$176.00
Purchase #7	$48.97	11.389%	$54.5472	$54.55	$54.55	$54.50
7 purchase totals =	$920.99		$1,017.7090	$1,017.70	$1,017.65	$1,017.60