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	$123.82	13.833%	$140.948	$140.95	$140.95	$140.90
Purchase #2	$244.34	6.326%	$259.7969	$259.80	$259.80	$259.80
Purchase #3	$37.70	4.802%	$39.5104	$39.51	$39.50	$39.50
Purchase #4	$57.76	12.567%	$65.0187	$65.02	$65.00	$65.00
Purchase #5	$228.87	10.662%	$253.2721	$253.27	$253.25	$253.30
Purchase #6	$90.62	8.704%	$98.5076	$98.51	$98.50	$98.50
Purchase #7	$226.31	12.226%	$253.9787	$253.98	$254.00	$254.00
7 purchase totals =	$1,009.42		$1,111.0324	$1,111.04	$1,111.00	$1,111.00