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	$66.77	7.330%	$71.6642	$71.66	$71.65	$71.70
Purchase #2	$110.91	7.859%	$119.6264	$119.63	$119.65	$119.60
Purchase #3	$69.37	3.673%	$71.918	$71.92	$71.90	$71.90
Purchase #4	$119.99	6.122%	$127.3358	$127.34	$127.35	$127.30
Purchase #5	$147.41	10.493%	$162.8777	$162.88	$162.90	$162.90
Purchase #6	$237.66	6.610%	$253.3693	$253.37	$253.35	$253.40
Purchase #7	$226.43	6.602%	$241.3789	$241.38	$241.40	$241.40
7 purchase totals =	$978.54		$1,048.1703	$1,048.18	$1,048.20	$1,048.20