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	$234.41	12.434%	$263.5565	$263.56	$263.55	$263.60
Purchase #2	$206.60	4.635%	$216.1759	$216.18	$216.20	$216.20
Purchase #3	$171.28	11.456%	$190.9018	$190.90	$190.90	$190.90
Purchase #4	$54.61	4.495%	$57.0647	$57.06	$57.05	$57.10
Purchase #5	$244.94	9.360%	$267.8664	$267.87	$267.85	$267.90
Purchase #6	$167.87	10.416%	$185.3553	$185.36	$185.35	$185.40
Purchase #7	$231.91	10.625%	$256.5504	$256.55	$256.55	$256.60
7 purchase totals =	$1,311.62		$1,437.4710	$1,437.48	$1,437.45	$1,437.70