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	$76.28	13.156%	$86.3154	$86.32	$86.30	$86.30
Purchase #2	$214.98	7.790%	$231.7269	$231.73	$231.75	$231.70
Purchase #3	$52.89	3.203%	$54.5841	$54.58	$54.60	$54.60
Purchase #4	$242.65	11.361%	$270.2175	$270.22	$270.20	$270.20
Purchase #5	$41.99	8.287%	$45.4697	$45.47	$45.45	$45.50
Purchase #6	$228.49	13.171%	$258.5844	$258.58	$258.60	$258.60
Purchase #7	$115.78	3.343%	$119.6505	$119.65	$119.65	$119.70
7 purchase totals =	$973.06		$1,066.5485	$1,066.55	$1,066.55	$1,066.60