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	$186.60	3.833%	$193.7524	$193.75	$193.75	$193.80
Purchase #2	$86.62	3.385%	$89.5521	$89.55	$89.55	$89.60
Purchase #3	$105.34	6.792%	$112.4947	$112.49	$112.50	$112.50
Purchase #4	$122.26	7.617%	$131.5725	$131.57	$131.55	$131.60
Purchase #5	$166.73	11.414%	$185.7606	$185.76	$185.75	$185.80
Purchase #6	$103.57	12.515%	$116.5318	$116.53	$116.55	$116.50
Purchase #7	$201.66	4.188%	$210.1055	$210.11	$210.10	$210.10
7 purchase totals =	$972.78		$1,039.7696	$1,039.76	$1,039.75	$1,039.90