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	$116.43	6.700%	$124.2308	$124.23	$124.25	$124.20
Purchase #2	$12.44	13.695%	$14.1437	$14.14	$14.15	$14.10
Purchase #3	$53.59	11.304%	$59.6478	$59.65	$59.65	$59.60
Purchase #4	$150.27	5.734%	$158.8865	$158.89	$158.90	$158.90
Purchase #5	$127.82	11.684%	$142.7545	$142.75	$142.75	$142.80
Purchase #6	$236.34	3.490%	$244.5883	$244.59	$244.60	$244.60
Purchase #7	$162.73	7.209%	$174.4612	$174.46	$174.45	$174.50
7 purchase totals =	$859.62		$918.7128	$918.71	$918.75	$918.70