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	$133.69	6.799%	$142.7796	$142.78	$142.80	$142.80
Purchase #2	$106.83	4.537%	$111.6769	$111.68	$111.70	$111.70
Purchase #3	$36.58	13.595%	$41.5531	$41.55	$41.55	$41.60
Purchase #4	$9.82	3.301%	$10.1442	$10.14	$10.15	$10.10
Purchase #5	$38.53	9.457%	$42.1738	$42.17	$42.15	$42.20
Purchase #6	$59.91	3.498%	$62.0057	$62.01	$62.00	$62.00
Purchase #7	$45.60	4.263%	$47.5439	$47.54	$47.55	$47.50
7 purchase totals =	$430.96		$457.8772	$457.87	$457.90	$457.90