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	$116.41	10.280%	$128.3769	$128.38	$128.40	$128.40
Purchase #2	$174.47	5.169%	$183.4884	$183.49	$183.50	$183.50
Purchase #3	$152.39	5.288%	$160.4484	$160.45	$160.45	$160.40
Purchase #4	$57.94	4.548%	$60.5751	$60.58	$60.60	$60.60
Purchase #5	$135.49	6.172%	$143.8524	$143.85	$143.85	$143.90
Purchase #6	$50.35	12.759%	$56.7742	$56.77	$56.75	$56.80
Purchase #7	$245.26	9.873%	$269.4745	$269.47	$269.45	$269.50
7 purchase totals =	$932.31		$1,002.9899	$1,002.99	$1,003.00	$1,003.10