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	$234.37	5.306%	$246.8057	$246.81	$246.80	$246.80
Purchase #2	$92.64	7.679%	$99.7538	$99.75	$99.75	$99.80
Purchase #3	$128.84	6.751%	$137.538	$137.54	$137.55	$137.50
Purchase #4	$143.83	6.857%	$153.6924	$153.69	$153.70	$153.70
Purchase #5	$247.43	3.790%	$256.8076	$256.81	$256.80	$256.80
Purchase #6	$76.83	10.665%	$85.0239	$85.02	$85.00	$85.00
Purchase #7	$41.80	12.259%	$46.9243	$46.92	$46.90	$46.90
7 purchase totals =	$965.74		$1,026.5457	$1,026.54	$1,026.50	$1,026.50