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	$96.65	13.628%	$109.8215	$109.82	$109.80	$109.80
Purchase #2	$137.79	10.528%	$152.2965	$152.30	$152.30	$152.30
Purchase #3	$164.37	3.228%	$169.6759	$169.68	$169.70	$169.70
Purchase #4	$13.75	11.294%	$15.3029	$15.30	$15.30	$15.30
Purchase #5	$210.54	12.113%	$236.0427	$236.04	$236.05	$236.00
Purchase #6	$99.89	9.564%	$109.4435	$109.44	$109.45	$109.40
Purchase #7	$205.36	7.138%	$220.0186	$220.02	$220.00	$220.00
7 purchase totals =	$928.35		$1,012.6016	$1,012.60	$1,012.60	$1,012.50