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	$181.88	4.678%	$190.3883	$190.39	$190.40	$190.40
Purchase #2	$154.50	13.247%	$174.9666	$174.97	$174.95	$175.00
Purchase #3	$78.57	10.295%	$86.6588	$86.66	$86.65	$86.70
Purchase #4	$245.80	6.517%	$261.8188	$261.82	$261.80	$261.80
Purchase #5	$52.41	10.192%	$57.7516	$57.75	$57.75	$57.80
Purchase #6	$125.79	11.845%	$140.6898	$140.69	$140.70	$140.70
Purchase #7	$163.64	13.144%	$185.1488	$185.15	$185.15	$185.10
7 purchase totals =	$1,002.59		$1,097.4227	$1,097.43	$1,097.40	$1,097.50