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	$57.26	3.800%	$59.4359	$59.44	$59.45	$59.40
Purchase #2	$132.82	5.774%	$140.489	$140.49	$140.50	$140.50
Purchase #3	$95.48	5.128%	$100.3762	$100.38	$100.40	$100.40
Purchase #4	$135.36	10.670%	$149.8029	$149.80	$149.80	$149.80
Purchase #5	$44.98	7.121%	$48.183	$48.18	$48.20	$48.20
Purchase #6	$174.38	12.481%	$196.1444	$196.14	$196.15	$196.10
Purchase #7	$142.79	12.360%	$160.4388	$160.44	$160.45	$160.40
7 purchase totals =	$783.07		$854.8702	$854.87	$854.95	$854.80