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	$196.40	8.672%	$213.4318	$213.43	$213.45	$213.40
Purchase #2	$120.30	13.231%	$136.2169	$136.22	$136.20	$136.20
Purchase #3	$93.90	9.695%	$103.0036	$103.00	$103.00	$103.00
Purchase #4	$241.47	10.822%	$267.6019	$267.60	$267.60	$267.60
Purchase #5	$191.87	8.845%	$208.8409	$208.84	$208.85	$208.80
Purchase #6	$98.34	13.315%	$111.434	$111.43	$111.45	$111.40
Purchase #7	$245.25	12.123%	$274.9817	$274.98	$275.00	$275.00
7 purchase totals =	$1,187.53		$1,315.5108	$1,315.50	$1,315.55	$1,315.40