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	$119.65	3.211%	$123.492	$123.49	$123.50	$123.50
Purchase #2	$40.55	11.148%	$45.0705	$45.07	$45.05	$45.10
Purchase #3	$167.43	3.531%	$173.342	$173.34	$173.35	$173.30
Purchase #4	$155.38	5.515%	$163.9492	$163.95	$163.95	$163.90
Purchase #5	$93.81	4.514%	$98.0446	$98.04	$98.05	$98.00
Purchase #6	$200.92	7.282%	$215.551	$215.55	$215.55	$215.60
Purchase #7	$170.53	8.850%	$185.6219	$185.62	$185.60	$185.60
7 purchase totals =	$948.27		$1,005.0712	$1,005.06	$1,005.05	$1,005.00