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	$154.39	9.366%	$168.8502	$168.85	$168.85	$168.90
Purchase #2	$49.57	5.210%	$52.1526	$52.15	$52.15	$52.20
Purchase #3	$248.53	3.376%	$256.9204	$256.92	$256.90	$256.90
Purchase #4	$76.31	12.770%	$86.0548	$86.05	$86.05	$86.10
Purchase #5	$139.74	12.142%	$156.7072	$156.71	$156.70	$156.70
Purchase #6	$173.49	5.802%	$183.5559	$183.56	$183.55	$183.60
Purchase #7	$112.76	4.585%	$117.93	$117.93	$117.95	$117.90
7 purchase totals =	$954.79		$1,022.1711	$1,022.17	$1,022.15	$1,022.30