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	$157.88	9.352%	$172.6449	$172.64	$172.65	$172.60
Purchase #2	$134.90	5.786%	$142.7053	$142.71	$142.70	$142.70
Purchase #3	$234.48	4.326%	$244.6236	$244.62	$244.60	$244.60
Purchase #4	$65.93	5.358%	$69.4625	$69.46	$69.45	$69.50
Purchase #5	$205.71	8.558%	$223.3147	$223.31	$223.30	$223.30
Purchase #6	$168.66	6.471%	$179.574	$179.57	$179.55	$179.60
Purchase #7	$34.46	3.638%	$35.7137	$35.71	$35.70	$35.70
7 purchase totals =	$1,002.02		$1,068.0387	$1,068.02	$1,067.95	$1,068.00