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	$27.56	4.520%	$28.8057	$28.81	$28.80	$28.80
Purchase #2	$22.90	13.346%	$25.9562	$25.96	$25.95	$26.00
Purchase #3	$66.59	9.403%	$72.8515	$72.85	$72.85	$72.90
Purchase #4	$182.64	12.197%	$204.9166	$204.92	$204.90	$204.90
Purchase #5	$76.89	7.795%	$82.8836	$82.88	$82.90	$82.90
Purchase #6	$164.89	9.859%	$181.1465	$181.15	$181.15	$181.10
Purchase #7	$86.84	5.759%	$91.8411	$91.84	$91.85	$91.80
7 purchase totals =	$628.31		$688.4012	$688.41	$688.40	$688.40