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	$55.96	5.850%	$59.2337	$59.23	$59.25	$59.20
Purchase #2	$127.76	12.867%	$144.1989	$144.20	$144.20	$144.20
Purchase #3	$117.54	6.195%	$124.8216	$124.82	$124.80	$124.80
Purchase #4	$46.64	11.283%	$51.9024	$51.90	$51.90	$51.90
Purchase #5	$25.95	6.152%	$27.5464	$27.55	$27.55	$27.50
Purchase #6	$7.76	11.638%	$8.6631	$8.66	$8.65	$8.70
Purchase #7	$19.25	11.432%	$21.4507	$21.45	$21.45	$21.50
7 purchase totals =	$400.86		$437.8168	$437.81	$437.80	$437.80