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	$173.61	13.798%	$197.5647	$197.56	$197.55	$197.60
Purchase #2	$35.31	8.750%	$38.3996	$38.40	$38.40	$38.40
Purchase #3	$73.79	8.599%	$80.1352	$80.14	$80.15	$80.10
Purchase #4	$50.86	10.598%	$56.2501	$56.25	$56.25	$56.30
Purchase #5	$152.85	13.484%	$173.4603	$173.46	$173.45	$173.50
Purchase #6	$94.73	5.361%	$99.8085	$99.81	$99.80	$99.80
Purchase #7	$123.58	12.699%	$139.2734	$139.27	$139.25	$139.30
7 purchase totals =	$704.73		$784.8918	$784.89	$784.85	$785.00