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	$114.65	3.124%	$118.2317	$118.23	$118.25	$118.20
Purchase #2	$53.91	6.701%	$57.5225	$57.52	$57.50	$57.50
Purchase #3	$164.89	6.696%	$175.931	$175.93	$175.95	$175.90
Purchase #4	$76.71	7.125%	$82.1756	$82.18	$82.20	$82.20
Purchase #5	$44.33	3.626%	$45.9374	$45.94	$45.95	$45.90
Purchase #6	$196.28	13.780%	$223.3274	$223.33	$223.35	$223.30
Purchase #7	$13.31	7.597%	$14.3212	$14.32	$14.30	$14.30
7 purchase totals =	$664.08		$717.4468	$717.45	$717.50	$717.30