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	$66.50	8.793%	$72.3473	$72.35	$72.35	$72.30
Purchase #2	$150.40	7.431%	$161.5762	$161.58	$161.60	$161.60
Purchase #3	$105.28	9.641%	$115.43	$115.43	$115.45	$115.40
Purchase #4	$98.75	13.259%	$111.8433	$111.84	$111.85	$111.80
Purchase #5	$183.38	7.635%	$197.3811	$197.38	$197.40	$197.40
Purchase #6	$185.97	5.507%	$196.2114	$196.21	$196.20	$196.20
Purchase #7	$191.67	13.531%	$217.6049	$217.60	$217.60	$217.60
7 purchase totals =	$981.95		$1,072.3942	$1,072.39	$1,072.45	$1,072.30