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	$83.50	11.328%	$92.9589	$92.96	$92.95	$93.00
Purchase #2	$35.62	12.498%	$40.0718	$40.07	$40.05	$40.10
Purchase #3	$92.49	9.497%	$101.2738	$101.27	$101.25	$101.30
Purchase #4	$24.36	4.463%	$25.4472	$25.45	$25.45	$25.40
Purchase #5	$198.87	4.800%	$208.4158	$208.42	$208.40	$208.40
Purchase #6	$112.62	13.609%	$127.9465	$127.95	$127.95	$127.90
Purchase #7	$243.56	11.843%	$272.4048	$272.40	$272.40	$272.40
7 purchase totals =	$791.02		$868.5188	$868.52	$868.45	$868.50