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	$6.75	10.519%	$7.46	$7.46	$7.45	$7.50
Purchase #2	$72.46	13.376%	$82.1522	$82.15	$82.15	$82.20
Purchase #3	$239.89	8.808%	$261.0195	$261.02	$261.00	$261.00
Purchase #4	$234.72	11.561%	$261.856	$261.86	$261.85	$261.90
Purchase #5	$214.69	5.212%	$225.8796	$225.88	$225.90	$225.90
Purchase #6	$81.43	6.529%	$86.7466	$86.75	$86.75	$86.70
Purchase #7	$196.84	6.522%	$209.6779	$209.68	$209.70	$209.70
7 purchase totals =	$1,046.78		$1,134.7918	$1,134.80	$1,134.80	$1,134.90