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	$227.49	11.431%	$253.4944	$253.49	$253.50	$253.50
Purchase #2	$81.30	3.197%	$83.8992	$83.90	$83.90	$83.90
Purchase #3	$185.46	3.559%	$192.0605	$192.06	$192.05	$192.10
Purchase #4	$70.76	3.142%	$72.9833	$72.98	$73.00	$73.00
Purchase #5	$93.83	6.869%	$100.2752	$100.28	$100.30	$100.30
Purchase #6	$239.65	6.462%	$255.1362	$255.14	$255.15	$255.10
Purchase #7	$222.66	6.686%	$237.547	$237.55	$237.55	$237.50
7 purchase totals =	$1,121.15		$1,195.3958	$1,195.40	$1,195.45	$1,195.40