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	$109.98	4.115%	$114.5057	$114.51	$114.50	$114.50
Purchase #2	$101.45	3.659%	$105.1621	$105.16	$105.15	$105.20
Purchase #3	$250.61	4.334%	$261.4714	$261.47	$261.45	$261.50
Purchase #4	$196.69	11.483%	$219.2759	$219.28	$219.30	$219.30
Purchase #5	$181.86	5.841%	$192.4824	$192.48	$192.50	$192.50
Purchase #6	$127.97	10.691%	$141.6513	$141.65	$141.65	$141.70
Purchase #7	$225.74	10.461%	$249.3547	$249.35	$249.35	$249.40
7 purchase totals =	$1,194.30		$1,283.9035	$1,283.90	$1,283.90	$1,284.10