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	$93.40	11.863%	$104.48	$104.48	$104.50	$104.50
Purchase #2	$165.71	8.397%	$179.6247	$179.62	$179.60	$179.60
Purchase #3	$133.37	3.289%	$137.7565	$137.76	$137.75	$137.80
Purchase #4	$13.80	8.561%	$14.9814	$14.98	$15.00	$15.00
Purchase #5	$212.62	11.181%	$236.393	$236.39	$236.40	$236.40
Purchase #6	$209.82	6.231%	$222.8939	$222.89	$222.90	$222.90
Purchase #7	$101.97	12.106%	$114.3145	$114.31	$114.30	$114.30
7 purchase totals =	$930.69		$1,010.4440	$1,010.43	$1,010.45	$1,010.50