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	$151.26	8.312%	$163.8327	$163.83	$163.85	$163.80
Purchase #2	$64.97	10.604%	$71.8594	$71.86	$71.85	$71.90
Purchase #3	$43.37	5.198%	$45.6244	$45.62	$45.60	$45.60
Purchase #4	$40.48	8.390%	$43.8763	$43.88	$43.90	$43.90
Purchase #5	$78.35	10.223%	$86.3597	$86.36	$86.35	$86.40
Purchase #6	$196.54	9.447%	$215.1071	$215.11	$215.10	$215.10
Purchase #7	$245.83	9.496%	$269.174	$269.17	$269.15	$269.20
7 purchase totals =	$820.80		$895.8336	$895.83	$895.80	$895.90