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	$77.78	5.857%	$82.3356	$82.34	$82.35	$82.30
Purchase #2	$56.53	8.755%	$61.4792	$61.48	$61.50	$61.50
Purchase #3	$210.28	13.471%	$238.6068	$238.61	$238.60	$238.60
Purchase #4	$140.34	12.441%	$157.7997	$157.80	$157.80	$157.80
Purchase #5	$148.82	12.581%	$167.543	$167.54	$167.55	$167.50
Purchase #6	$185.54	11.189%	$206.3001	$206.30	$206.30	$206.30
Purchase #7	$199.56	13.663%	$226.8259	$226.83	$226.85	$226.80
7 purchase totals =	$1,018.85		$1,140.8903	$1,140.90	$1,140.95	$1,140.80