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	$127.67	5.454%	$134.6331	$134.63	$134.65	$134.60
Purchase #2	$186.32	7.565%	$200.4151	$200.42	$200.40	$200.40
Purchase #3	$105.86	3.315%	$109.3693	$109.37	$109.35	$109.40
Purchase #4	$141.48	12.240%	$158.7972	$158.80	$158.80	$158.80
Purchase #5	$103.59	11.376%	$115.3744	$115.37	$115.35	$115.40
Purchase #6	$161.26	10.751%	$178.5971	$178.60	$178.60	$178.60
Purchase #7	$212.29	8.118%	$229.5237	$229.52	$229.50	$229.50
7 purchase totals =	$1,038.47		$1,126.7099	$1,126.71	$1,126.65	$1,126.70