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	$177.62	4.640%	$185.8616	$185.86	$185.85	$185.90
Purchase #2	$43.55	12.550%	$49.0155	$49.02	$49.00	$49.00
Purchase #3	$60.61	6.239%	$64.3915	$64.39	$64.40	$64.40
Purchase #4	$64.55	5.186%	$67.8976	$67.90	$67.90	$67.90
Purchase #5	$156.27	7.849%	$168.5356	$168.54	$168.55	$168.50
Purchase #6	$91.41	13.644%	$103.882	$103.88	$103.90	$103.90
Purchase #7	$226.64	8.370%	$245.6098	$245.61	$245.60	$245.60
7 purchase totals =	$820.65		$885.1936	$885.20	$885.20	$885.20