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	$67.77	6.150%	$71.9379	$71.94	$71.95	$71.90
Purchase #2	$135.45	8.133%	$146.4661	$146.47	$146.45	$146.50
Purchase #3	$180.76	8.605%	$196.3144	$196.31	$196.30	$196.30
Purchase #4	$40.41	7.229%	$43.3312	$43.33	$43.35	$43.30
Purchase #5	$44.60	9.851%	$48.9935	$48.99	$49.00	$49.00
Purchase #6	$96.69	5.241%	$101.7575	$101.76	$101.75	$101.80
Purchase #7	$106.62	6.379%	$113.4213	$113.42	$113.40	$113.40
7 purchase totals =	$672.30		$722.2219	$722.22	$722.20	$722.20