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	$143.87	4.805%	$150.783	$150.78	$150.80	$150.80
Purchase #2	$91.30	9.185%	$99.6859	$99.69	$99.70	$99.70
Purchase #3	$189.63	5.808%	$200.6437	$200.64	$200.65	$200.60
Purchase #4	$109.95	5.693%	$116.2095	$116.21	$116.20	$116.20
Purchase #5	$141.96	13.164%	$160.6476	$160.65	$160.65	$160.60
Purchase #6	$167.83	13.108%	$189.8292	$189.83	$189.85	$189.80
Purchase #7	$108.81	3.341%	$112.4453	$112.45	$112.45	$112.40
7 purchase totals =	$953.35		$1,030.2442	$1,030.25	$1,030.30	$1,030.10