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	$105.67	13.383%	$119.8118	$119.81	$119.80	$119.80
Purchase #2	$94.56	9.238%	$103.2955	$103.30	$103.30	$103.30
Purchase #3	$117.88	11.617%	$131.5741	$131.57	$131.55	$131.60
Purchase #4	$42.30	11.857%	$47.3155	$47.32	$47.30	$47.30
Purchase #5	$93.60	12.525%	$105.3234	$105.32	$105.30	$105.30
Purchase #6	$56.55	12.350%	$63.5339	$63.53	$63.55	$63.50
Purchase #7	$190.60	10.478%	$210.5711	$210.57	$210.55	$210.60
7 purchase totals =	$701.16		$781.4253	$781.42	$781.35	$781.40