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	$246.64	3.396%	$255.0159	$255.02	$255.00	$255.00
Purchase #2	$145.81	3.513%	$150.9323	$150.93	$150.95	$150.90
Purchase #3	$68.71	12.645%	$77.3984	$77.40	$77.40	$77.40
Purchase #4	$203.37	6.201%	$215.981	$215.98	$216.00	$216.00
Purchase #5	$52.55	13.441%	$59.6132	$59.61	$59.60	$59.60
Purchase #6	$71.44	8.472%	$77.4924	$77.49	$77.50	$77.50
Purchase #7	$183.71	3.246%	$189.6732	$189.67	$189.65	$189.70
7 purchase totals =	$972.23		$1,026.1064	$1,026.10	$1,026.10	$1,026.10