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	$78.95	4.390%	$82.4159	$82.42	$82.40	$82.40
Purchase #2	$76.70	11.720%	$85.6892	$85.69	$85.70	$85.70
Purchase #3	$175.41	7.822%	$189.1306	$189.13	$189.15	$189.10
Purchase #4	$183.55	12.638%	$206.747	$206.75	$206.75	$206.70
Purchase #5	$203.81	9.853%	$223.8914	$223.89	$223.90	$223.90
Purchase #6	$151.67	13.346%	$171.9119	$171.91	$171.90	$171.90
Purchase #7	$37.41	7.592%	$40.2502	$40.25	$40.25	$40.30
7 purchase totals =	$907.50		$1,000.0362	$1,000.04	$1,000.05	$1,000.00