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	$121.97	4.418%	$127.3586	$127.36	$127.35	$127.40
Purchase #2	$218.36	13.721%	$248.3212	$248.32	$248.30	$248.30
Purchase #3	$147.55	11.547%	$164.5876	$164.59	$164.60	$164.60
Purchase #4	$153.78	7.858%	$165.864	$165.86	$165.85	$165.90
Purchase #5	$135.25	12.692%	$152.4159	$152.42	$152.40	$152.40
Purchase #6	$157.34	6.367%	$167.3578	$167.36	$167.35	$167.40
Purchase #7	$123.29	6.330%	$131.0943	$131.09	$131.10	$131.10
7 purchase totals =	$1,057.54		$1,156.9994	$1,157.00	$1,156.95	$1,157.10