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	$55.42	10.515%	$61.2474	$61.25	$61.25	$61.20
Purchase #2	$237.83	3.166%	$245.3597	$245.36	$245.35	$245.40
Purchase #3	$65.36	11.633%	$72.9633	$72.96	$72.95	$73.00
Purchase #4	$101.35	11.570%	$113.0762	$113.08	$113.10	$113.10
Purchase #5	$165.46	11.828%	$185.0306	$185.03	$185.05	$185.00
Purchase #6	$217.80	7.693%	$234.5554	$234.56	$234.55	$234.60
Purchase #7	$150.67	11.377%	$167.8117	$167.81	$167.80	$167.80
7 purchase totals =	$993.89		$1,080.0443	$1,080.05	$1,080.05	$1,080.10