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	$31.52	7.557%	$33.902	$33.90	$33.90	$33.90
Purchase #2	$163.79	7.691%	$176.3871	$176.39	$176.40	$176.40
Purchase #3	$115.93	13.221%	$131.2571	$131.26	$131.25	$131.30
Purchase #4	$53.41	3.214%	$55.1266	$55.13	$55.15	$55.10
Purchase #5	$162.99	10.408%	$179.954	$179.95	$179.95	$180.00
Purchase #6	$214.60	4.186%	$223.5832	$223.58	$223.60	$223.60
Purchase #7	$112.53	13.217%	$127.4031	$127.40	$127.40	$127.40
7 purchase totals =	$854.77		$927.6131	$927.61	$927.65	$927.70