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	$108.59	4.719%	$113.7144	$113.71	$113.70	$113.70
Purchase #2	$172.35	7.400%	$185.1039	$185.10	$185.10	$185.10
Purchase #3	$196.60	12.157%	$220.5007	$220.50	$220.50	$220.50
Purchase #4	$79.28	8.105%	$85.7056	$85.71	$85.70	$85.70
Purchase #5	$167.63	8.213%	$181.3975	$181.40	$181.40	$181.40
Purchase #6	$235.86	8.797%	$256.6086	$256.61	$256.60	$256.60
Purchase #7	$46.38	3.817%	$48.1503	$48.15	$48.15	$48.20
7 purchase totals =	$1,006.69		$1,091.1810	$1,091.18	$1,091.15	$1,091.20