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	$149.53	3.811%	$155.2286	$155.23	$155.25	$155.20
Purchase #2	$179.57	3.137%	$185.2031	$185.20	$185.20	$185.20
Purchase #3	$150.88	11.136%	$167.682	$167.68	$167.70	$167.70
Purchase #4	$136.71	10.211%	$150.6695	$150.67	$150.65	$150.70
Purchase #5	$213.96	11.413%	$238.3793	$238.38	$238.40	$238.40
Purchase #6	$37.80	3.575%	$39.1514	$39.15	$39.15	$39.20
Purchase #7	$57.77	9.223%	$63.0981	$63.10	$63.10	$63.10
7 purchase totals =	$926.22		$999.4120	$999.41	$999.45	$999.50