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	$151.59	13.705%	$172.3654	$172.37	$172.35	$172.40
Purchase #2	$198.65	11.410%	$221.316	$221.32	$221.30	$221.30
Purchase #3	$191.29	3.567%	$198.1133	$198.11	$198.10	$198.10
Purchase #4	$96.71	13.803%	$110.0589	$110.06	$110.05	$110.10
Purchase #5	$134.34	12.106%	$150.6032	$150.60	$150.60	$150.60
Purchase #6	$171.92	10.850%	$190.5733	$190.57	$190.55	$190.60
Purchase #7	$81.55	3.732%	$84.5934	$84.59	$84.60	$84.60
7 purchase totals =	$1,026.05		$1,127.6235	$1,127.62	$1,127.55	$1,127.70