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	$182.70	7.766%	$196.8885	$196.89	$196.90	$196.90
Purchase #2	$103.44	4.744%	$108.3472	$108.35	$108.35	$108.30
Purchase #3	$176.60	10.246%	$194.6944	$194.69	$194.70	$194.70
Purchase #4	$187.83	6.717%	$200.4465	$200.45	$200.45	$200.40
Purchase #5	$185.56	3.872%	$192.7449	$192.74	$192.75	$192.70
Purchase #6	$19.67	6.651%	$20.9783	$20.98	$21.00	$21.00
Purchase #7	$135.53	3.726%	$140.5798	$140.58	$140.60	$140.60
7 purchase totals =	$991.33		$1,054.6796	$1,054.68	$1,054.75	$1,054.60