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	$43.41	11.367%	$48.3444	$48.34	$48.35	$48.30
Purchase #2	$73.91	11.136%	$82.1406	$82.14	$82.15	$82.10
Purchase #3	$25.58	6.468%	$27.2345	$27.23	$27.25	$27.20
Purchase #4	$174.25	13.641%	$198.0194	$198.02	$198.00	$198.00
Purchase #5	$91.40	11.736%	$102.1267	$102.13	$102.15	$102.10
Purchase #6	$135.86	4.661%	$142.1924	$142.19	$142.20	$142.20
Purchase #7	$113.37	12.574%	$127.6251	$127.63	$127.65	$127.60
7 purchase totals =	$657.78		$727.6831	$727.68	$727.75	$727.50