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	13.125%	$178.1379	$178.14	$178.15	$178.10
Purchase #2	$91.88	3.641%	$95.2254	$95.23	$95.25	$95.20
Purchase #3	$67.66	7.814%	$72.947	$72.95	$72.95	$72.90
Purchase #4	$101.32	9.534%	$110.9798	$110.98	$111.00	$111.00
Purchase #5	$182.27	4.572%	$190.6034	$190.60	$190.60	$190.60
Purchase #6	$97.92	11.590%	$109.2689	$109.27	$109.25	$109.30
Purchase #7	$82.47	10.698%	$91.2926	$91.29	$91.30	$91.30
7 purchase totals =	$780.99		$848.4550	$848.46	$848.50	$848.40