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	$228.39	9.729%	$250.6101	$250.61	$250.60	$250.60
Purchase #2	$48.33	6.558%	$51.4995	$51.50	$51.50	$51.50
Purchase #3	$46.29	7.712%	$49.8599	$49.86	$49.85	$49.90
Purchase #4	$87.27	3.480%	$90.307	$90.31	$90.30	$90.30
Purchase #5	$164.51	11.132%	$182.8233	$182.82	$182.80	$182.80
Purchase #6	$43.45	7.857%	$46.8639	$46.86	$46.85	$46.90
Purchase #7	$238.55	10.497%	$263.5906	$263.59	$263.60	$263.60
7 purchase totals =	$856.79		$935.5543	$935.55	$935.50	$935.60