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	$75.59	8.832%	$82.2661	$82.27	$82.25	$82.30
Purchase #2	$47.31	11.754%	$52.8708	$52.87	$52.85	$52.90
Purchase #3	$18.36	8.784%	$19.9727	$19.97	$19.95	$20.00
Purchase #4	$247.73	5.127%	$260.4311	$260.43	$260.45	$260.40
Purchase #5	$203.50	10.872%	$225.6245	$225.62	$225.60	$225.60
Purchase #6	$166.88	10.790%	$184.8864	$184.89	$184.90	$184.90
Purchase #7	$232.57	9.524%	$254.72	$254.72	$254.70	$254.70
7 purchase totals =	$991.94		$1,080.7716	$1,080.77	$1,080.70	$1,080.80