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	$230.63	6.593%	$245.8354	$245.84	$245.85	$245.80
Purchase #2	$47.49	8.421%	$51.4891	$51.49	$51.50	$51.50
Purchase #3	$216.33	11.762%	$241.7747	$241.77	$241.75	$241.80
Purchase #4	$67.57	7.228%	$72.454	$72.45	$72.45	$72.50
Purchase #5	$189.84	3.275%	$196.0573	$196.06	$196.05	$196.10
Purchase #6	$202.31	10.170%	$222.8849	$222.88	$222.90	$222.90
Purchase #7	$241.34	10.840%	$267.5013	$267.50	$267.50	$267.50
7 purchase totals =	$1,195.51		$1,297.9967	$1,297.99	$1,298.00	$1,298.10