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	$220.85	9.721%	$242.3188	$242.32	$242.30	$242.30
Purchase #2	$90.48	9.493%	$99.0693	$99.07	$99.05	$99.10
Purchase #3	$162.36	6.239%	$172.4896	$172.49	$172.50	$172.50
Purchase #4	$143.63	13.139%	$162.5015	$162.50	$162.50	$162.50
Purchase #5	$21.32	4.546%	$22.2892	$22.29	$22.30	$22.30
Purchase #6	$249.77	12.418%	$280.7864	$280.79	$280.80	$280.80
Purchase #7	$107.84	5.111%	$113.3517	$113.35	$113.35	$113.40
7 purchase totals =	$996.25		$1,092.8065	$1,092.81	$1,092.80	$1,092.90