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	$178.50	10.146%	$196.6106	$196.61	$196.60	$196.60
Purchase #2	$34.30	6.741%	$36.6122	$36.61	$36.60	$36.60
Purchase #3	$75.90	3.472%	$78.5352	$78.54	$78.55	$78.50
Purchase #4	$157.33	5.506%	$165.9926	$165.99	$166.00	$166.00
Purchase #5	$193.85	12.529%	$218.1375	$218.14	$218.15	$218.10
Purchase #6	$213.65	3.600%	$221.3414	$221.34	$221.35	$221.30
Purchase #7	$216.36	12.748%	$243.9416	$243.94	$243.95	$243.90
7 purchase totals =	$1,069.89		$1,161.1711	$1,161.17	$1,161.20	$1,161.00