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	$159.55	12.405%	$179.3422	$179.34	$179.35	$179.30
Purchase #2	$223.76	8.369%	$242.4865	$242.49	$242.50	$242.50
Purchase #3	$230.52	9.806%	$253.1248	$253.12	$253.10	$253.10
Purchase #4	$86.77	3.382%	$89.7046	$89.70	$89.70	$89.70
Purchase #5	$30.83	8.391%	$33.4169	$33.42	$33.40	$33.40
Purchase #6	$82.35	10.495%	$90.9926	$90.99	$91.00	$91.00
Purchase #7	$174.91	7.223%	$187.5437	$187.54	$187.55	$187.50
7 purchase totals =	$988.69		$1,076.6113	$1,076.60	$1,076.60	$1,076.50