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	$157.47	9.272%	$172.0706	$172.07	$172.05	$172.10
Purchase #2	$141.80	7.853%	$152.9356	$152.94	$152.95	$152.90
Purchase #3	$116.52	7.869%	$125.689	$125.69	$125.70	$125.70
Purchase #4	$248.37	8.416%	$269.2728	$269.27	$269.25	$269.30
Purchase #5	$80.79	10.617%	$89.3675	$89.37	$89.35	$89.40
Purchase #6	$100.70	3.106%	$103.8277	$103.83	$103.85	$103.80
Purchase #7	$148.92	7.786%	$160.5149	$160.51	$160.50	$160.50
7 purchase totals =	$994.57		$1,073.6781	$1,073.68	$1,073.65	$1,073.70