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	$169.98	13.452%	$192.8457	$192.85	$192.85	$192.80
Purchase #2	$34.33	3.839%	$35.6479	$35.65	$35.65	$35.60
Purchase #3	$245.91	5.333%	$259.0244	$259.02	$259.00	$259.00
Purchase #4	$169.59	8.852%	$184.6021	$184.60	$184.60	$184.60
Purchase #5	$33.27	9.815%	$36.5355	$36.54	$36.55	$36.50
Purchase #6	$53.60	4.262%	$55.8844	$55.88	$55.90	$55.90
Purchase #7	$19.72	11.136%	$21.916	$21.92	$21.90	$21.90
7 purchase totals =	$726.40		$786.4560	$786.46	$786.45	$786.30