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	$157.76	10.519%	$174.3548	$174.35	$174.35	$174.40
Purchase #2	$206.99	13.368%	$234.6604	$234.66	$234.65	$234.70
Purchase #3	$150.50	11.354%	$167.5878	$167.59	$167.60	$167.60
Purchase #4	$131.34	4.213%	$136.8734	$136.87	$136.85	$136.90
Purchase #5	$127.94	5.143%	$134.52	$134.52	$134.50	$134.50
Purchase #6	$124.56	4.741%	$130.4654	$130.47	$130.45	$130.50
Purchase #7	$98.41	7.313%	$105.6067	$105.61	$105.60	$105.60
7 purchase totals =	$997.50		$1,084.0685	$1,084.07	$1,084.00	$1,084.20