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	$81.27	9.566%	$89.0443	$89.04	$89.05	$89.00
Purchase #2	$144.27	12.153%	$161.8031	$161.80	$161.80	$161.80
Purchase #3	$106.31	11.480%	$118.5144	$118.51	$118.50	$118.50
Purchase #4	$189.71	11.112%	$210.7906	$210.79	$210.80	$210.80
Purchase #5	$175.48	13.177%	$198.603	$198.60	$198.60	$198.60
Purchase #6	$164.39	12.865%	$185.5388	$185.54	$185.55	$185.50
Purchase #7	$87.78	12.465%	$98.7218	$98.72	$98.70	$98.70
7 purchase totals =	$949.21		$1,063.0160	$1,063.00	$1,063.00	$1,062.90