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	$140.39	12.864%	$158.4498	$158.45	$158.45	$158.40
Purchase #2	$110.74	3.525%	$114.6436	$114.64	$114.65	$114.60
Purchase #3	$157.77	4.511%	$164.887	$164.89	$164.90	$164.90
Purchase #4	$89.79	12.529%	$101.0398	$101.04	$101.05	$101.00
Purchase #5	$188.67	13.306%	$213.7744	$213.77	$213.75	$213.80
Purchase #6	$205.37	6.326%	$218.3617	$218.36	$218.35	$218.40
Purchase #7	$161.58	11.119%	$179.5461	$179.55	$179.55	$179.50
7 purchase totals =	$1,054.31		$1,150.7024	$1,150.70	$1,150.70	$1,150.60