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	$56.71	5.623%	$59.8988	$59.90	$59.90	$59.90
Purchase #2	$6.42	13.636%	$7.2954	$7.30	$7.30	$7.30
Purchase #3	$166.42	10.617%	$184.0888	$184.09	$184.10	$184.10
Purchase #4	$119.30	13.157%	$134.9963	$135.00	$135.00	$135.00
Purchase #5	$79.33	3.809%	$82.3517	$82.35	$82.35	$82.40
Purchase #6	$143.55	5.172%	$150.9744	$150.97	$150.95	$151.00
Purchase #7	$122.88	7.833%	$132.5052	$132.51	$132.50	$132.50
7 purchase totals =	$694.61		$752.1106	$752.12	$752.10	$752.20