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	$169.60	8.323%	$183.7158	$183.72	$183.70	$183.70
Purchase #2	$205.74	10.316%	$226.9641	$226.96	$226.95	$227.00
Purchase #3	$40.77	3.267%	$42.102	$42.10	$42.10	$42.10
Purchase #4	$39.59	3.283%	$40.8897	$40.89	$40.90	$40.90
Purchase #5	$38.83	11.801%	$43.4123	$43.41	$43.40	$43.40
Purchase #6	$127.47	4.161%	$132.774	$132.77	$132.75	$132.80
Purchase #7	$229.81	6.651%	$245.0947	$245.09	$245.10	$245.10
7 purchase totals =	$851.81		$914.9526	$914.94	$914.90	$915.00