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	$227.56	10.698%	$251.9044	$251.90	$251.90	$251.90
Purchase #2	$86.83	3.478%	$89.8499	$89.85	$89.85	$89.80
Purchase #3	$87.45	8.311%	$94.718	$94.72	$94.70	$94.70
Purchase #4	$229.79	12.177%	$257.7715	$257.77	$257.75	$257.80
Purchase #5	$186.72	8.707%	$202.9777	$202.98	$203.00	$203.00
Purchase #6	$34.54	6.610%	$36.8231	$36.82	$36.80	$36.80
Purchase #7	$118.53	7.412%	$127.3154	$127.32	$127.30	$127.30
7 purchase totals =	$971.42		$1,061.3600	$1,061.36	$1,061.30	$1,061.30