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	$232.92	12.250%	$261.4527	$261.45	$261.45	$261.50
Purchase #2	$183.49	7.292%	$196.8701	$196.87	$196.85	$196.90
Purchase #3	$153.28	8.813%	$166.7886	$166.79	$166.80	$166.80
Purchase #4	$164.27	8.807%	$178.7373	$178.74	$178.75	$178.70
Purchase #5	$109.30	3.725%	$113.3714	$113.37	$113.35	$113.40
Purchase #6	$10.47	13.685%	$11.9028	$11.90	$11.90	$11.90
Purchase #7	$191.36	3.581%	$198.2126	$198.21	$198.20	$198.20
7 purchase totals =	$1,045.09		$1,127.3355	$1,127.33	$1,127.30	$1,127.40