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	$74.83	4.710%	$78.3545	$78.35	$78.35	$78.40
Purchase #2	$150.51	3.783%	$156.2038	$156.20	$156.20	$156.20
Purchase #3	$151.47	13.365%	$171.714	$171.71	$171.70	$171.70
Purchase #4	$36.69	7.803%	$39.5529	$39.55	$39.55	$39.60
Purchase #5	$144.26	8.397%	$156.3735	$156.37	$156.35	$156.40
Purchase #6	$185.79	13.652%	$211.1541	$211.15	$211.15	$211.20
Purchase #7	$222.63	6.447%	$236.983	$236.98	$237.00	$237.00
7 purchase totals =	$966.18		$1,050.3358	$1,050.31	$1,050.30	$1,050.50