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	$125.41	12.544%	$141.1414	$141.14	$141.15	$141.10
Purchase #2	$218.46	3.136%	$225.3109	$225.31	$225.30	$225.30
Purchase #3	$229.27	12.775%	$258.5592	$258.56	$258.55	$258.60
Purchase #4	$212.48	5.704%	$224.5999	$224.60	$224.60	$224.60
Purchase #5	$136.37	3.793%	$141.5425	$141.54	$141.55	$141.50
Purchase #6	$127.69	7.654%	$137.4634	$137.46	$137.45	$137.50
Purchase #7	$190.62	12.209%	$213.8928	$213.89	$213.90	$213.90
7 purchase totals =	$1,240.30		$1,342.5101	$1,342.50	$1,342.50	$1,342.50