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	$93.48	9.404%	$102.2709	$102.27	$102.25	$102.30
Purchase #2	$123.53	10.359%	$136.3265	$136.33	$136.35	$136.30
Purchase #3	$131.45	10.353%	$145.059	$145.06	$145.05	$145.10
Purchase #4	$148.54	5.176%	$156.2284	$156.23	$156.25	$156.20
Purchase #5	$214.48	4.691%	$224.5413	$224.54	$224.55	$224.50
Purchase #6	$70.50	11.284%	$78.4552	$78.46	$78.45	$78.50
Purchase #7	$179.25	9.251%	$195.8324	$195.83	$195.85	$195.80
7 purchase totals =	$961.23		$1,038.7137	$1,038.72	$1,038.75	$1,038.70