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	$47.76	7.703%	$51.439	$51.44	$51.45	$51.40
Purchase #2	$38.92	3.789%	$40.3947	$40.39	$40.40	$40.40
Purchase #3	$172.30	9.320%	$188.3584	$188.36	$188.35	$188.40
Purchase #4	$212.38	6.252%	$225.658	$225.66	$225.65	$225.70
Purchase #5	$114.54	11.678%	$127.916	$127.92	$127.90	$127.90
Purchase #6	$133.26	7.139%	$142.7734	$142.77	$142.75	$142.80
Purchase #7	$231.45	10.648%	$256.0948	$256.09	$256.10	$256.10
7 purchase totals =	$950.61		$1,032.6343	$1,032.63	$1,032.60	$1,032.70