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	$84.78	8.580%	$92.0541	$92.05	$92.05	$92.10
Purchase #2	$126.89	10.758%	$140.5408	$140.54	$140.55	$140.50
Purchase #3	$151.77	8.828%	$165.1683	$165.17	$165.15	$165.20
Purchase #4	$204.93	8.328%	$221.9966	$222.00	$222.00	$222.00
Purchase #5	$108.62	6.391%	$115.5619	$115.56	$115.55	$115.60
Purchase #6	$141.71	6.744%	$151.2669	$151.27	$151.25	$151.30
Purchase #7	$203.55	9.361%	$222.6043	$222.60	$222.60	$222.60
7 purchase totals =	$1,022.25		$1,109.1929	$1,109.19	$1,109.15	$1,109.30