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	$18.43	3.357%	$19.0487	$19.05	$19.05	$19.00
Purchase #2	$31.60	13.321%	$35.8094	$35.81	$35.80	$35.80
Purchase #3	$166.44	11.290%	$185.2311	$185.23	$185.25	$185.20
Purchase #4	$64.77	10.570%	$71.6162	$71.62	$71.60	$71.60
Purchase #5	$47.38	11.693%	$52.9201	$52.92	$52.90	$52.90
Purchase #6	$231.39	10.532%	$255.76	$255.76	$255.75	$255.80
Purchase #7	$48.68	10.831%	$53.9525	$53.95	$53.95	$54.00
7 purchase totals =	$608.69		$674.3380	$674.34	$674.30	$674.30