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	$210.93	10.372%	$232.8077	$232.81	$232.80	$232.80
Purchase #2	$86.37	6.210%	$91.7336	$91.73	$91.75	$91.70
Purchase #3	$200.94	13.830%	$228.73	$228.73	$228.75	$228.70
Purchase #4	$125.56	10.712%	$139.01	$139.01	$139.00	$139.00
Purchase #5	$224.73	13.612%	$255.3202	$255.32	$255.30	$255.30
Purchase #6	$150.58	6.370%	$160.1719	$160.17	$160.15	$160.20
Purchase #7	$42.83	5.252%	$45.0794	$45.08	$45.10	$45.10
7 purchase totals =	$1,041.94		$1,152.8528	$1,152.85	$1,152.85	$1,152.80