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	$112.42	10.229%	$123.9194	$123.92	$123.90	$123.90
Purchase #2	$148.27	9.745%	$162.7189	$162.72	$162.70	$162.70
Purchase #3	$229.82	13.585%	$261.041	$261.04	$261.05	$261.00
Purchase #4	$73.70	10.472%	$81.4179	$81.42	$81.40	$81.40
Purchase #5	$107.68	12.173%	$120.7879	$120.79	$120.80	$120.80
Purchase #6	$100.43	4.574%	$105.0237	$105.02	$105.00	$105.00
Purchase #7	$241.90	3.208%	$249.6602	$249.66	$249.65	$249.70
7 purchase totals =	$1,014.22		$1,104.5690	$1,104.57	$1,104.50	$1,104.50