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	$74.51	4.789%	$78.0783	$78.08	$78.10	$78.10
Purchase #2	$82.71	8.640%	$89.8561	$89.86	$89.85	$89.90
Purchase #3	$38.31	11.868%	$42.8566	$42.86	$42.85	$42.90
Purchase #4	$216.84	9.667%	$237.8019	$237.80	$237.80	$237.80
Purchase #5	$151.42	9.870%	$166.3652	$166.37	$166.35	$166.40
Purchase #6	$171.52	9.255%	$187.3942	$187.39	$187.40	$187.40
Purchase #7	$220.27	6.711%	$235.0523	$235.05	$235.05	$235.10
7 purchase totals =	$955.58		$1,037.4046	$1,037.41	$1,037.40	$1,037.60