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	$241.81	9.342%	$264.3999	$264.40	$264.40	$264.40
Purchase #2	$123.34	6.600%	$131.4804	$131.48	$131.50	$131.50
Purchase #3	$41.56	4.676%	$43.5033	$43.50	$43.50	$43.50
Purchase #4	$133.87	8.870%	$145.7443	$145.74	$145.75	$145.70
Purchase #5	$110.63	12.149%	$124.0704	$124.07	$124.05	$124.10
Purchase #6	$160.94	3.553%	$166.6582	$166.66	$166.65	$166.70
Purchase #7	$177.33	4.865%	$185.9571	$185.96	$185.95	$186.00
7 purchase totals =	$989.48		$1,061.8136	$1,061.81	$1,061.80	$1,061.90