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	$98.29	13.662%	$111.7184	$111.72	$111.70	$111.70
Purchase #2	$198.78	5.325%	$209.365	$209.37	$209.35	$209.40
Purchase #3	$43.68	9.179%	$47.6894	$47.69	$47.70	$47.70
Purchase #4	$101.82	12.572%	$114.6208	$114.62	$114.60	$114.60
Purchase #5	$200.34	6.141%	$212.6429	$212.64	$212.65	$212.60
Purchase #6	$110.85	8.330%	$120.0838	$120.08	$120.10	$120.10
Purchase #7	$106.54	4.453%	$111.2842	$111.28	$111.30	$111.30
7 purchase totals =	$860.30		$927.4045	$927.40	$927.40	$927.40