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	$177.38	11.695%	$198.1246	$198.12	$198.10	$198.10
Purchase #2	$109.30	5.451%	$115.2579	$115.26	$115.25	$115.30
Purchase #3	$114.76	8.182%	$124.1497	$124.15	$124.15	$124.10
Purchase #4	$125.57	12.784%	$141.6229	$141.62	$141.60	$141.60
Purchase #5	$170.60	8.517%	$185.13	$185.13	$185.15	$185.10
Purchase #6	$71.40	9.288%	$78.0316	$78.03	$78.05	$78.00
Purchase #7	$99.72	8.590%	$108.2859	$108.29	$108.30	$108.30
7 purchase totals =	$868.73		$950.6026	$950.60	$950.60	$950.50