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	$193.97	3.372%	$200.5107	$200.51	$200.50	$200.50
Purchase #2	$170.49	11.540%	$190.1645	$190.16	$190.15	$190.20
Purchase #3	$103.29	9.739%	$113.3494	$113.35	$113.35	$113.30
Purchase #4	$210.91	5.532%	$222.5775	$222.58	$222.60	$222.60
Purchase #5	$239.51	12.493%	$269.432	$269.43	$269.45	$269.40
Purchase #6	$190.76	13.145%	$215.8354	$215.84	$215.85	$215.80
Purchase #7	$181.95	4.585%	$190.2924	$190.29	$190.30	$190.30
7 purchase totals =	$1,290.88		$1,402.1619	$1,402.16	$1,402.20	$1,402.10