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	$174.36	9.156%	$190.3244	$190.32	$190.30	$190.30
Purchase #2	$39.65	8.195%	$42.8993	$42.90	$42.90	$42.90
Purchase #3	$246.95	3.546%	$255.7068	$255.71	$255.70	$255.70
Purchase #4	$164.80	13.363%	$186.8222	$186.82	$186.80	$186.80
Purchase #5	$28.37	13.678%	$32.2504	$32.25	$32.25	$32.30
Purchase #6	$21.64	8.720%	$23.527	$23.53	$23.55	$23.50
Purchase #7	$209.56	13.423%	$237.6892	$237.69	$237.70	$237.70
7 purchase totals =	$885.33		$969.2193	$969.22	$969.20	$969.20