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	$144.34	4.419%	$150.7184	$150.72	$150.70	$150.70
Purchase #2	$223.84	11.740%	$250.1188	$250.12	$250.10	$250.10
Purchase #3	$244.48	7.144%	$261.9457	$261.95	$261.95	$261.90
Purchase #4	$144.62	4.330%	$150.882	$150.88	$150.90	$150.90
Purchase #5	$63.81	7.514%	$68.6047	$68.60	$68.60	$68.60
Purchase #6	$134.69	5.709%	$142.3795	$142.38	$142.40	$142.40
Purchase #7	$142.45	9.804%	$156.4158	$156.42	$156.40	$156.40
7 purchase totals =	$1,098.23		$1,181.0649	$1,181.07	$1,181.05	$1,181.00