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	$117.75	8.509%	$127.7693	$127.77	$127.75	$127.80
Purchase #2	$242.57	8.483%	$263.1472	$263.15	$263.15	$263.10
Purchase #3	$202.50	6.340%	$215.3385	$215.34	$215.35	$215.30
Purchase #4	$250.76	5.254%	$263.9349	$263.93	$263.95	$263.90
Purchase #5	$106.44	9.838%	$116.9116	$116.91	$116.90	$116.90
Purchase #6	$159.32	3.739%	$165.277	$165.28	$165.30	$165.30
Purchase #7	$42.53	4.755%	$44.5523	$44.55	$44.55	$44.60
7 purchase totals =	$1,121.87		$1,196.9308	$1,196.93	$1,196.95	$1,196.90