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	$217.79	9.478%	$238.4321	$238.43	$238.45	$238.40
Purchase #2	$175.94	9.573%	$192.7827	$192.78	$192.80	$192.80
Purchase #3	$135.53	12.824%	$152.9104	$152.91	$152.90	$152.90
Purchase #4	$190.52	13.140%	$215.5543	$215.55	$215.55	$215.60
Purchase #5	$92.48	6.297%	$98.3035	$98.30	$98.30	$98.30
Purchase #6	$39.44	13.546%	$44.7825	$44.78	$44.80	$44.80
Purchase #7	$173.27	4.410%	$180.9112	$180.91	$180.90	$180.90
7 purchase totals =	$1,024.97		$1,123.6767	$1,123.66	$1,123.70	$1,123.70