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	$114.86	11.705%	$128.3044	$128.30	$128.30	$128.30
Purchase #2	$64.75	10.323%	$71.4341	$71.43	$71.45	$71.40
Purchase #3	$78.89	9.331%	$86.2512	$86.25	$86.25	$86.30
Purchase #4	$166.42	7.119%	$178.2674	$178.27	$178.25	$178.30
Purchase #5	$107.74	10.826%	$119.4039	$119.40	$119.40	$119.40
Purchase #6	$156.58	11.416%	$174.4552	$174.46	$174.45	$174.50
Purchase #7	$224.71	10.588%	$248.5023	$248.50	$248.50	$248.50
7 purchase totals =	$913.95		$1,006.6185	$1,006.61	$1,006.60	$1,006.70