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	$131.46	13.189%	$148.7983	$148.80	$148.80	$148.80
Purchase #2	$78.90	6.363%	$83.9204	$83.92	$83.90	$83.90
Purchase #3	$142.79	5.206%	$150.2236	$150.22	$150.20	$150.20
Purchase #4	$209.43	6.697%	$223.4555	$223.46	$223.45	$223.50
Purchase #5	$129.70	11.203%	$144.2303	$144.23	$144.25	$144.20
Purchase #6	$47.41	4.382%	$49.4875	$49.49	$49.50	$49.50
Purchase #7	$190.82	10.177%	$210.2398	$210.24	$210.25	$210.20
7 purchase totals =	$930.51		$1,010.3554	$1,010.36	$1,010.35	$1,010.30