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	$204.33	6.696%	$218.0119	$218.01	$218.00	$218.00
Purchase #2	$6.31	11.651%	$7.0452	$7.05	$7.05	$7.00
Purchase #3	$206.68	3.326%	$213.5542	$213.55	$213.55	$213.60
Purchase #4	$142.83	13.715%	$162.4191	$162.42	$162.40	$162.40
Purchase #5	$69.78	11.847%	$78.0468	$78.05	$78.05	$78.00
Purchase #6	$75.30	10.141%	$82.9362	$82.94	$82.95	$82.90
Purchase #7	$185.86	11.539%	$207.3064	$207.31	$207.30	$207.30
7 purchase totals =	$891.09		$969.3198	$969.33	$969.30	$969.20