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	$214.29	11.199%	$238.2883	$238.29	$238.30	$238.30
Purchase #2	$204.74	10.650%	$226.5448	$226.54	$226.55	$226.50
Purchase #3	$135.56	9.779%	$148.8164	$148.82	$148.80	$148.80
Purchase #4	$31.28	11.713%	$34.9438	$34.94	$34.95	$34.90
Purchase #5	$50.95	9.570%	$55.8259	$55.83	$55.85	$55.80
Purchase #6	$241.95	9.322%	$264.5046	$264.50	$264.50	$264.50
Purchase #7	$42.46	12.593%	$47.807	$47.81	$47.80	$47.80
7 purchase totals =	$921.23		$1,016.7308	$1,016.73	$1,016.75	$1,016.60