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	$193.87	3.173%	$200.0215	$200.02	$200.00	$200.00
Purchase #2	$60.30	8.612%	$65.493	$65.49	$65.50	$65.50
Purchase #3	$41.27	9.175%	$45.0565	$45.06	$45.05	$45.10
Purchase #4	$5.79	13.353%	$6.5631	$6.56	$6.55	$6.60
Purchase #5	$180.64	10.723%	$200.01	$200.01	$200.00	$200.00
Purchase #6	$216.50	12.172%	$242.8524	$242.85	$242.85	$242.90
Purchase #7	$219.93	9.832%	$241.5535	$241.55	$241.55	$241.60
7 purchase totals =	$918.30		$1,001.5500	$1,001.54	$1,001.50	$1,001.70