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	$223.32	6.335%	$237.4673	$237.47	$237.45	$237.50
Purchase #2	$72.74	8.497%	$78.9207	$78.92	$78.90	$78.90
Purchase #3	$158.68	9.415%	$173.6197	$173.62	$173.60	$173.60
Purchase #4	$174.98	6.700%	$186.7037	$186.70	$186.70	$186.70
Purchase #5	$172.35	12.582%	$194.0351	$194.04	$194.05	$194.00
Purchase #6	$117.89	4.690%	$123.419	$123.42	$123.40	$123.40
Purchase #7	$47.42	9.502%	$51.9258	$51.93	$51.95	$51.90
7 purchase totals =	$967.38		$1,046.0913	$1,046.10	$1,046.05	$1,046.00