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	$90.80	3.641%	$94.106	$94.11	$94.10	$94.10
Purchase #2	$116.93	5.578%	$123.4524	$123.45	$123.45	$123.50
Purchase #3	$250.81	13.651%	$285.0481	$285.05	$285.05	$285.00
Purchase #4	$203.70	7.783%	$219.554	$219.55	$219.55	$219.60
Purchase #5	$119.76	3.823%	$124.3384	$124.34	$124.35	$124.30
Purchase #6	$67.77	7.578%	$72.9056	$72.91	$72.90	$72.90
Purchase #7	$83.43	5.343%	$87.8877	$87.89	$87.90	$87.90
7 purchase totals =	$933.20		$1,007.2922	$1,007.30	$1,007.30	$1,007.30