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	$153.86	9.719%	$168.8137	$168.81	$168.80	$168.80
Purchase #2	$178.72	6.263%	$189.9132	$189.91	$189.90	$189.90
Purchase #3	$215.61	4.741%	$225.8321	$225.83	$225.85	$225.80
Purchase #4	$171.98	12.544%	$193.5532	$193.55	$193.55	$193.60
Purchase #5	$114.81	13.727%	$130.57	$130.57	$130.55	$130.60
Purchase #6	$11.64	4.155%	$12.1236	$12.12	$12.10	$12.10
Purchase #7	$85.71	5.264%	$90.2218	$90.22	$90.20	$90.20
7 purchase totals =	$932.33		$1,011.0276	$1,011.01	$1,010.95	$1,011.00