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	$165.82	6.488%	$176.5784	$176.58	$176.60	$176.60
Purchase #2	$92.61	6.588%	$98.7111	$98.71	$98.70	$98.70
Purchase #3	$115.28	3.763%	$119.618	$119.62	$119.60	$119.60
Purchase #4	$210.76	7.160%	$225.8504	$225.85	$225.85	$225.90
Purchase #5	$196.94	13.244%	$223.0227	$223.02	$223.00	$223.00
Purchase #6	$55.61	12.549%	$62.5885	$62.59	$62.60	$62.60
Purchase #7	$241.77	13.805%	$275.1463	$275.15	$275.15	$275.10
7 purchase totals =	$1,078.79		$1,181.5154	$1,181.52	$1,181.50	$1,181.50