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	$229.59	7.738%	$247.3557	$247.36	$247.35	$247.40
Purchase #2	$124.59	7.484%	$133.9143	$133.91	$133.90	$133.90
Purchase #3	$161.53	11.703%	$180.4339	$180.43	$180.45	$180.40
Purchase #4	$51.30	7.839%	$55.3214	$55.32	$55.30	$55.30
Purchase #5	$50.99	6.822%	$54.4685	$54.47	$54.45	$54.50
Purchase #6	$94.56	5.373%	$99.6407	$99.64	$99.65	$99.60
Purchase #7	$217.42	6.777%	$232.1546	$232.15	$232.15	$232.20
7 purchase totals =	$929.98		$1,003.2891	$1,003.28	$1,003.25	$1,003.30