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	$216.46	10.280%	$238.7121	$238.71	$238.70	$238.70
Purchase #2	$239.54	10.859%	$265.5516	$265.55	$265.55	$265.60
Purchase #3	$208.99	4.709%	$218.8313	$218.83	$218.85	$218.80
Purchase #4	$35.89	8.377%	$38.8965	$38.90	$38.90	$38.90
Purchase #5	$236.63	3.208%	$244.2211	$244.22	$244.20	$244.20
Purchase #6	$128.31	11.284%	$142.7885	$142.79	$142.80	$142.80
Purchase #7	$39.40	8.487%	$42.7439	$42.74	$42.75	$42.70
7 purchase totals =	$1,105.22		$1,191.7450	$1,191.74	$1,191.75	$1,191.70